1
Q
What is the most common thyroid disease in dogs?
A
Canine Hypothyroidism
It is one of the most common endocrine diseases in dogs, with a prevalence of 0.2 - 0.8 %.
2
Q
The thyroid gland of dogs consists of how many lobes? What are the the three tissues related to the thyroid gland?
A
2 separate lobes
follicles = functional unit
interstitial C cells = secrete calcitonin
Parathyroid tissue
Each lobe is located on either side of the trachea at the 1st or 2nd tracheal ring.
3
Q
What is the functional unit of the thyroid gland?
A
Follicles
Each follicle is lined by a single layer of thyroid epithelium and contains colloid.
4
Q
What does the lumen of follicles primarily contain?
A
Colloid that primarily contains thyroglobulin
Thyroglobulin is a large glycoprotein containing iodotyrosine, components of thyroid hormone.
5
Q
What do parafollicular cells (C cells) synthesize and secrete?
A
Calcitonin
These cells lie in the interstitium between the follicles.
6
Q
What are the active thyroid hormones produced by the thyroid gland?
A
- T4: Thyroxine
- T3: Triiodothyronine
T3 is about 4x as potent as T4 and is present in smaller quantities.
7
Q
Iodine is required for the formation of thyroid hormones. Where is iodine converted to iodide?
A
In the small intestines
Iodide is then transported to the thyroid follicles.
8
Q
What is the process of iodide trapping?
A
Concentrating the iodide in the follicular cells using NIS; directly influenced by TSH
-NIS transports I across basolateral membrane, then transported across apical membrane via pendrin
NIS co-transports one iodide along with 2 sodium ions across the basolateral membrane.
9
Q
What enzyme promotes the oxidation of iodide ions?
A
Thyroid peroxidase (TPO)
This enzyme converts iodide ions to an oxidized form of iodine.
10
Q
What is the binding of oxidized iodine with tyrosine amino acid within thyroglobulin called?
A
Organification of thyroglobulin
Tyrosine is iodized to monoiodotyrosine (MIT) and then to diiodotyrosine (DIT).
11
Q
What are the components of T3 and T4?
A
- T3: MIT + DIT
- T4: DIT + DIT
Synthesized thyroid hormones are stored in the colloid of follicles.
12
Q
What happens during thyroid hormone secretion?
A
T4 and T3 are cleaved from thyroglobulin and released into the blood stream
This process involves pinocytic vesicles and lysosomal digestion.
13
Q
What percentage of iodinated tyrosine in thyroglobulin never becomes thyroid hormones?
A
75%
They remain as MIT and DIT and are recycled within the cells.
14
Q
How do thyroid hormones enter tissue cells? What is the major one?
A
Mediated by transporter proteins; thyroxine binding globulin
T3 enters cells more rapidly and is more potent than T4.
15
Q
What is the general effect of thyroid hormones on the body?
A
Activate nuclear transcription of a large number of genes
-metabolism, growth
-CNS dependent
-tissue turnover
-+ inotrope, + chronotrope
-cholesterol synthesis/ metablism
-+/- erythropoiesis
This results in a generalized increase in functional activity throughout the body.
16
Q
What regulates thyroid hormone secretion?
A
Negative feedback of TRH and TSH via T3/T4
TRH from the hypothalamus stimulates TSH secretion from the anterior pituitary.
17
Q
What is congenital hypothyroidism?
A
Results from thyroid hypoplasia or aplasia, dysgenesis, or dyshormonogenesis
Central - TSH or TRH deficiency
TSH deficiency is common in pituitary dwarfism
It is significantly less common than acquired hypothyroidism.
18
Q
A
19
Q
What is the most common cause of acquired hypothyroidism?
A
Primary thyroid disease
Histologically, lymphocytic thyroiditis and thyroid atrophy are common.
20
Q
What is lymphocytic thyroiditis characterized by?
A
Destructive autoimmune process
It involves infiltration of the thyroid gland by lymphocytes and macrophages.
21
Q
Which breeds have a high prevalence of TgAA positive and increased risk for developing hypothyroidism?
A
- English Setter
- Golden Retriever
- Rhodesian Ridgeback
- Cocker Spaniel
- Boxer
These breeds are at a higher risk for hypothyroidism.
22
Q
What was the annual prevalence of hypothyroidism found in a retrospective study in the UK?
A
0.23%
The study identified 24 predisposed and 9 protected breeds.
23
Q
What factors increase the odds of a dog living with a diagnosis of hypothyroidism?
A
- Being a purebred dog
- Being insured
- Having BW above the breed-sex mean
- Increasing age
- Being neutered
- Rising adult BW
These factors were identified in a retrospective study evaluating hypothyroidism in Eurasian dogs.
24
Q
In the study on Eurasian dogs, what was the overall prevalence of hypothyroidism?
A
3.9%
The study also found a prevalence of positive TgAA at 7.9% on initial exam.
25
What laboratory indicators are used to classify **hypothyroidism** in dogs?
* Combined decrease in TT4
* Increase in TSH in serum
## Footnote
Hypothyroidism can be classified as TgAA positive or TgAA negative.
26
What is the **sensitivity** and **specificity** of TgAA to predict the presence of hypothyroidism?
* Sensitivity: 44.8%
* Specificity: 93.6%
* PPV: 22%
* NPV: 97.7%
## Footnote
These values indicate the effectiveness of TgAA in diagnosing hypothyroidism.
27
What are the **most common clinical signs** of hypothyroidism in dogs?
* Lethargy
* Weight gain
* Exercise intolerance
* Mental dullness
* Cold intolerance
* Generalized weakness
* Shivering
## Footnote
These signs are often related to metabolic and dermatological abnormalities.
28
What are the **dermatological features** associated with hypothyroidism in dogs?
* Hair thinning
* Dry coarse hair coat
* Alopecia (flanks and thighs)
* Failure to regrow hair after clipping
* Dry scaly skin
* Seborrhea
* Hyperpigmentation
## Footnote
These features occur in about 80% of affected dogs.
29
True or false: **Hypothyroidism** can cause a non-pitting puffy appearance of the skin known as **myxedema**.
TRUE
## Footnote
Myxedema is characterized by accumulation of hyaluronic acid in the dermis.
30
What are the **cardiovascular features** associated with hypothyroidism in dogs?
* Low voltage R waves
* Inverted T waves
* Sinus bradycardia
* Bradydysrhythmias
## Footnote
These features can theoretically impair cardiac function but rarely do.
31
What is the **mean age of diagnosis** for hypothyroidism in dogs?
About 7 years
## Footnote
Hypothyroidism can occur in dogs of any breed but typically affects purebred dogs.
32
What is the **relationship** between hypothyroidism and **Addison's disease** in dogs?
* Hypothyroidism should be suspected in dogs with Addison's disease
* Particularly if there is a poor response to mineralocorticoid therapy
## Footnote
This relationship is particularly noted in dogs with concurrent endocrine disorders.
33
What are common **clinicopathological changes** observed in hypothyroid dogs?
* Anemia
* Hypercholesterolemia
* Hypertriglyceridemia
* Increased CK
* Increased fructosamine
## Footnote
None of these changes are specific to hypothyroidism.
34
What is the **significance** of increased CK in hypothyroid dogs?
Usually doesn't exceed twice the upper limit of the reference range
## Footnote
Increased CK may result from decreased metabolism or hypothyroid-induced myopathy.
35
What is the **predictive value** of TgAA for hypothyroidism in the Eurasian dog breed?
High
## Footnote
The presence of TgAA is a significant indicator for hypothyroidism or developing hypothyroidism.
36
What are the **neuromuscular features** associated with hypothyroidism in dogs?
* Facial nerve paralysis
* Laryngeal paralysis
* Megaesophagus
* Peripheral vestibular disease
* Generalized weakness
## Footnote
Limited evidence exists for a direct causal effect.
37
What is **congenital hypothyroidism** characterized by in dogs?
* Disproportionate dwarfism
* Delayed dental eruption
* Macroglossia
* Square trunk and short limbs
## Footnote
Signs become evident by about 8 weeks of age.
38
What are the **ophthalmic features** associated with hypothyroidism in dogs?
* Arcus lipoides
* KCS (Keratoconjunctivitis sicca)
## Footnote
Arcus lipoides is characterized by lipid infiltration in the cornea.
39
What is the **diagnostic accuracy** of SDMA in dogs with hypothyroid dysfunction?
Requires additional evaluation
## Footnote
SDMA con. were rarely above the upper limit of RI when the highest cut off (< 18 ug/dl) was employed.
40
Name the **common assays** used for thyroid function testing.
* TT4
* TT3
* fT4
* TSH
* TgAA
* T4AA
* T3AA
## Footnote
No single test has 100% diagnostic sensitivity.
41
What **non-thyroidal factors** can influence thyroid testing results?
* Breed
* Gender
* Age
* Neuter status
* Body condition
* Physical activity
## Footnote
These factors can adversely affect diagnostic specificity.
42
True or false: **Assay methodology** can influence the accuracy of thyroid test results.
TRUE
## Footnote
Different methodologies may yield varying results.
43
What are the **total thyroid hormone assays** designed to measure?
* Circulating protein bound concentration
* Free concentration
## Footnote
RIA (radioimmunoassay) is the standard reference technique for TT4 and TT3.
44
What is the **gold standard** for measuring free (unbound) hormone fT4?
* Equilibrium dialysis
* Ultrafiltration-based methods
## Footnote
These methods eliminate interference from circulating thyroid hormone antibodies or other binding proteins.
45
What is a concern regarding **chemiluminescent immunoassays (CLIA)** for measuring fT4?
* More false negative results compared to fT4 measured by ED
* Less ability to differentiate hypothyroid from non-thyroidal illness
## Footnote
Sensitivities of CLIA for fT4 were 62% for humans and 75% for veterinary patients.
46
What is the **effect of drug therapy** on thyroid hormone concentration?
* Can alter TT4 levels
* May mimic primary hypothyroidism
## Footnote
Drugs like glucocorticoids and sulfonamide antibiotics can significantly affect thyroid function.
47
What is the **sensitivity** of total T4 concentration as a screening test for hypothyroidism?
89-100%
## Footnote
Poor specificity (73-82%) means TT4 should not be used as the sole diagnostic test.
48
What does a **positive thyroglobulin autoantibody (TgAA)** indicate?
Indirectly supports a diagnosis of hypothyroidism
## Footnote
50% of hypothyroid dogs have TgAA.
49
What is the **recommended protocol** for TSH stimulation testing?
* Administration of a supraphysiologic dose of TSH
* Measure TT4 before and 6 hours after administration
## Footnote
This test is rarely done in the USA due to expense.
50
What is the expected TT4 level in **hypothyroid dogs** after TSH stimulation?
TT4 < 20 nmol/L (0.7 mcg/dl)
## Footnote
A recent study showed post TT4 con. < 1.7 mcg/dl had sensitivity of 100% and specificity of 93% for diagnosing hypothyroidism.
51
How many dogs were included in the **cross-sectional study**?
114 dogs
## Footnote
The study classified 40 dogs as hypothyroid and 74 as euthyroid.
52
What were the **post TSH T4 cut-offs** that showed sensitivity and specificity?
* 1.3 mcg/dl: Sensitivity 92.5%, Specificity 97.3%
* 1.7 mcg/dl: Sensitivity 100%, Specificity 93.2%
## Footnote
These cut-offs are critical for diagnosing hypothyroidism in dogs.
53
What is the **negative predictive value** of post TSH T4 levels of > 1.7 mcg/dl?
100%
## Footnote
This indicates that a level above this threshold reliably rules out hypothyroidism.
54
What is the **positive predictive value** of post TSH T4 levels of < 1.3 mcg/dl?
94.9%
## Footnote
This suggests a high likelihood of hypothyroidism when levels are below this threshold.
55
What was the **area under the ROC curve** for post-TSH T4?
0.99
## Footnote
This indicates excellent diagnostic performance.
56
What is the **safe and reliable** dose of recombinant human TSH for a TSH stim test?
75 ug/dog
## Footnote
This test can differentiate between hypothyroid and euthyroid dogs.
57
A post stim T4 concentration of > 1.7 ug/dl is suggestive of __________.
normal thyroid function
## Footnote
This level indicates that the thyroid is functioning properly.
58
What are the **characteristics** of thyroid lobes in hypothyroid dogs observed via ultrasound?
* Less echogenicity
* Irregular outline
* Small and more rounded
## Footnote
These features help in diagnosing hypothyroidism.
59
What is the **treatment of choice** for hypothyroid dogs?
Synthetic T4 (levothyroxine)
## Footnote
This is essential for lifelong thyroid hormone replacement therapy.
60
Why is the administration of **T3** not recommended for hypothyroid dogs?
* Circumvents normal physiological process
* Increases risk of thyrotoxicosis
* Requires multiple daily doses
## Footnote
T3 can lead to complications and is not suitable for dogs.
61
What is the recommended **dosage frequency** for T4 supplementation in dogs?
* SID (once daily)
* BID (twice daily)
## Footnote
The frequency may vary based on individual response and weight considerations.
62
What is the **starting dosage** of levothyroxine for hypothyroid dogs?
20 ug/kg PO q24h
## Footnote
This dosage is suitable for maintenance in 50% of dogs.
63
What are the **clinical signs** that may improve after thyroid hormone supplementation?
* Dullness and lethargy
* Weight loss
* Dermatological improvement
* Neurological improvement
## Footnote
These signs may take weeks to months to normalize.
64
What is the **monitoring** protocol after initiating levothyroxine supplementation?
Start 4 weeks after initiation unless signs persist
## Footnote
Monitoring includes evaluating TT4 levels to adjust dosage as needed.
65
What is the **prognosis** for dogs with hypothyroidism when treated appropriately?
Excellent prognosis
## Footnote
Most dogs respond well to treatment and show significant improvement.
66
What are the three layers of the adrenal cortex?
Zona glomerulosa, zona fasciculata, zona reticularis
67
Mnemonic for adrenal cortex layers from outer to inner.
Salt, Sugar, Sex
68
Which adrenal layer produces aldosterone?
Zona glomerulosa
69
Which adrenal layer produces cortisol?
Zona fasciculata
70
Which adrenal layer produces sex hormones?
Zona reticularis
71
All adrenal steroid hormones are derived from which precursor?
Cholesterol
72
The zona glomerulosa is rich in which enzyme?
Aldosterone synthase
73
Zona fasciculata and reticularis contain abundant ______ hydroxylase.
17‑alpha hydroxylase
74
Main regulator of cortisol secretion.
ACTH
75
Hormone released from hypothalamus that stimulates ACTH.
CRH
76
CRH is produced by which hypothalamic nucleus?
Paraventricular nucleus
77
ACTH is produced by which pituitary cells?
Corticotrophs
78
ACTH is derived from which precursor molecule?
Pro‑opiomelanocortin (POMC)
79
Two important fragments produced from POMC besides ACTH.
Melanocyte stimulating hormones (MSH)
80
Primary glucocorticoid produced in dogs.
Cortisol
81
Major metabolic effect of cortisol on glucose.
Increases gluconeogenesis
82
Effect of cortisol on insulin sensitivity.
Decreases insulin sensitivity
83
Cortisol promotes breakdown of which macromolecules?
Protein and fat
84
Protein catabolism caused by cortisol leads to what clinical sign?
Muscle wasting
85
Why do Cushingoid dogs develop a pot‑bellied appearance?
Muscle wasting, hepatomegaly, fat redistribution
86
Effect of cortisol on immune function.
Immunosuppression
87
Cortisol decreases leukocyte migration by reducing expression of what molecules?
Endothelial adhesion molecules
88
Classic leukogram seen with glucocorticoid excess.
Stress leukogram
89
Mnemonic for stress leukogram.
SMILE
90
SMILE: S stands for what?
Segmented neutrophilia
91
SMILE: M stands for what?
Monocytosis
92
SMILE: L stands for what?
Lymphopenia
93
SMILE: E stands for what?
Eosinopenia
94
Most common cause of canine Cushing’s disease.
Pituitary tumor
95
Percent of canine Cushing’s that is pituitary dependent.
~85%
96
Percent of canine Cushing’s that is adrenal dependent.
~15%
97
Most pituitary tumors causing Cushing’s are what type?
Adenomas
98
Definition of pituitary microadenoma.
<10 mm
99
Adrenal tumors causing Cushing’s are typically unilateral or bilateral?
Unilateral
100
Contralateral adrenal gland appearance in adrenal tumor Cushing’s.
Atrophied
101
Age group most commonly affected by Cushing’s.
Middle aged to older dogs
102
Percent of dogs with Cushing’s older than 6 years.
~90%
103
Common breeds predisposed to Cushing’s.
Poodles, Dachshunds, Terriers, Beagles
104
Classic '5 P's' of Cushing’s disease.
Polyuria, Polydipsia, Polyphagia, Panting, Pot‑bellied abdomen
105
Mechanism of PU/PD in Cushing’s.
ADH antagonism → nephrogenic DI
106
Cushing’s causes which type of hepatopathy?
Vacuolar hepatopathy
107
Most common dermatologic lesion in Cushing’s.
Alopecia
108
Mineral deposition in skin in Cushing’s.
Calcinosis cutis
109
Why are UTIs common in Cushing’s dogs?
Immunosuppression and dilute urine
110
Percent of Cushing’s dogs with UTIs.
~50%
111
Most common biochemical abnormality in Cushing’s.
Marked ALP elevation
112
Why is ALP high in Cushing’s?
Steroid‑induced ALP isoenzyme
113
ACTH stimulation test measures what?
Cortisol response to ACTH
114
Drug used for ACTH stimulation test.
Cosyntropin
115
Post‑ACTH cortisol >22 µg/dL suggests what disease?
Hyperadrenocorticism
116
ACTH stim test is the best test to diagnose which type of Cushing’s?
Iatrogenic Cushing’s
117
ACTH stim test is more specific or more sensitive?
More specific
118
Purpose of low‑dose dex suppression test.
Detect hyperadrenocorticism
119
Drug used in LDDST.
Dexamethasone
120
First step in interpreting LDDST.
Check 8‑hour cortisol
121
8‑hour cortisol >1.4 µg/dL suggests what?
Cushing’s disease
122
If cortisol suppresses at 4 hours in LDDST, diagnosis likely.
Pituitary dependent Cushing’s
123
Percent of PDH dogs that suppress in LDDST.
~65%
124
First‑line medical treatment for canine Cushing’s.
Trilostane
125
Mechanism of trilostane.
Inhibits 3‑beta hydroxysteroid dehydrogenase
126
Main adverse effect of trilostane.
Iatrogenic Addison’s
127
Monitoring test used during trilostane therapy.
ACTH stimulation test
128
Older drug that causes adrenal cortical necrosis.
Mitotane
129
Mitotane destroys which adrenal zones?
Zona fasciculata and reticularis
130
Addison’s disease causes deficiency of which hormones?
Glucocorticoids and mineralocorticoids
131
Percent of Addison’s cases that are primary.
~95%
132
Percent adrenal cortex destruction needed for Addison’s.
~90%
133
Classic electrolyte pattern of Addison’s.
Hyponatremia and hyperkalemia
134
Common sodium:potassium ratio suggesting Addison’s.
<27
135
Ratio strongly suggestive of Addison’s.
<20
136
Addison’s commonly causes what type of azotemia?
Prerenal
137
Why does Addison’s cause hypotension?
Loss of cortisol and aldosterone
138
Screening test to rule out Addison’s.
Baseline cortisol
139
Baseline cortisol >2 µg/dL rules out what disease?
Addison’s
140
If baseline cortisol <2 µg/dL, next diagnostic test.
ACTH stimulation test
141
ACTH stim result in Addison’s.
Flat cortisol response
142
Initial treatment for Addisonian crisis.
IV fluids
143
Glucocorticoid used initially in crisis because it does not interfere with cortisol assays.
Dexamethasone
144
Mineralocorticoid injection used in Addison’s.
DOCP
145
Common oral glucocorticoid used for maintenance.
Prednisone
146
Species most commonly affected by primary hyperaldosteronism.
Cats
147
Cause of primary hyperaldosteronism.
Adrenal tumor
148
Electrolyte abnormality most consistent with hyperaldosteronism.
Hypokalemia
149
Classic posture caused by hypokalemia in cats.
Ventral neck flexion
150
Common ophthalmic sign of feline hyperaldosteronism.
Retinal hemorrhage from hypertension
151
Surgical treatment of choice for unilateral hyperaldosteronism.
Adrenalectomy
152
Drug used to block aldosterone receptors.
Spironolactone
153
Tumor arising from adrenal medulla chromaffin cells.
Pheochromocytoma
154
Catecholamines are derived from which amino acid?
Tyrosine
155
Main catecholamines produced in adrenal medulla.
Epinephrine and norepinephrine
156
Major diagnostic metabolites measured for pheochromocytoma.
Metanephrine and normetanephrine
157
Clinical signs of pheochromocytoma are often what pattern?
Episodic
158
Two common cardiovascular signs of pheochromocytoma.
Hypertension and tachycardia
159
Pre‑operative drug given before adrenalectomy for pheochromocytoma.
Phenoxybenzamine
160
Phenoxybenzamine blocks which receptors?
Alpha adrenergic receptors
161
Adrenal mass found incidentally during imaging is called what?
Adrenal incidentaloma
162
Adrenal masses >2 cm are more likely to be what?
Malignant
163
Evaluation of adrenal incidentaloma should screen for which three endocrine diseases?
Cushing’s, pheochromocytoma, hyperaldosteronism
164
ACTH stim: baseline cortisol normal, post-ACTH exaggerated (>22 µg/dL). Diagnosis?
Hyperadrenocorticism
165
ACTH stim: baseline low, post-ACTH minimal response. Diagnosis?
Addison’s disease
166
ACTH stim: both baseline and post-ACTH suppressed in PU/PD dog on steroids. Diagnosis?
Iatrogenic Cushing’s
167
ACTH stim primarily evaluates which adrenal hormone?
Cortisol
168
ACTH stimulation test sensitivity compared to LDDST.
Lower sensitivity but higher specificity
169
LDDST: 8‑hour cortisol suppressed <1.4 µg/dL. Interpretation?
Normal (rules out Cushing’s)
170
LDDST: 8‑hour cortisol >1.4 µg/dL. Interpretation?
Cushing’s disease likely
171
LDDST: cortisol suppressed at 4 hr but escapes at 8 hr. Most likely diagnosis?
Pituitary‑dependent Cushing’s
172
LDDST: no suppression at 4 or 8 hr. Possible causes?
Adrenal tumor or non‑suppressing PDH
173
Why adrenal tumors rarely suppress in LDDST?
ACTH already suppressed by cortisol feedback
174
Dog with PU/PD, ALP 1500, dilute urine, stress leukogram. Top endocrine differential?
Cushing’s disease
175
Dog with vomiting, Na:K ratio 18, bradycardia. Top endocrine diagnosis?
Addison’s disease
176
Cat with hypokalemia and ventroflexion of neck. Endocrine disease?
Hyperaldosteronism
177
Dog with episodic hypertension and collapse plus adrenal mass. Diagnosis?
Pheochromocytoma
178
Dog with bilateral adrenal enlargement and ACTH high. Diagnosis?
Pituitary dependent Cushing’s
179
Hyponatremia + hyperkalemia endocrine disease.
Addison’s disease
180
Hypokalemia + hypertension in cat endocrine disease.
Hyperaldosteronism
181
Hyperglycemia + insulin resistance endocrine cause.
Cushing’s disease
182
Hypoglycemia + collapse endocrine differential.
Addison’s disease
183
Hyperlipidemia commonly seen in which endocrine disease?
Cushing’s disease
184
Trilostane MOA.
Inhibits 3‑beta hydroxysteroid dehydrogenase
185
Mitotane MOA.
Selective adrenal cortical necrosis
186
DOCP replaces which hormone?
Aldosterone
187
Spironolactone blocks which receptor?
Aldosterone receptor
188
Phenoxybenzamine blocks which receptor type?
Alpha adrenergic
189
Most common cause of Cushing’s disease in dogs.
Pituitary adenoma
190
Most common adrenal disease in cats.
Hyperaldosteronism
191
Most common cause of Addison’s disease in dogs.
Immune‑mediated adrenal destruction
192
Most dangerous complication of pheochromocytoma surgery.
Hypertensive crisis
193
Most common electrolyte abnormality in feline hyperaldosteronism.
Hypokalemia
194
Bilateral adrenal enlargement on ultrasound suggests.
Pituitary dependent Cushing’s
195
Unilateral adrenal mass with contralateral atrophy suggests.
Adrenal tumor Cushing’s
196
Adrenal mass invading vena cava suggests.
Pheochromocytoma
197
Adrenal incidentaloma >2 cm concern.
Malignancy risk
198
Best imaging modality for adrenal tumor staging.
CT scan
199
Why cortisol increases blood glucose.
Stimulates gluconeogenesis
200
Why cortisol causes muscle wasting.
Protein catabolism
201
Why cortisol suppresses immune response.
Reduces leukocyte migration
202
Why cortisol causes PU/PD.
ADH antagonism
203
Why aldosterone increases blood pressure.
Sodium and water retention
204
10‑year-old Dachshund with PU/PD, polyphagia, pot belly, ALP 1800, dilute urine. Most likely diagnosis?
Hyperadrenocorticism (Cushing's disease)
205
Dog with PU/PD and ALP elevation. LDDST 8‑hr cortisol = 6 µg/dL. Interpretation?
Positive for Cushing’s disease
206
Dog with Cushing's. LDDST shows cortisol suppression at 4 hr but escape at 8 hr. Likely type?
Pituitary‑dependent Cushing’s
207
Dog with Cushing's. LDDST shows no suppression at 4 or 8 hr. Possible causes?
Adrenal tumor or non‑suppressing PDH
208
Ultrasound shows unilateral adrenal mass and contralateral adrenal atrophy. Diagnosis?
Adrenal‑dependent hyperadrenocorticism
209
Bilateral adrenal enlargement on ultrasound in a Cushingoid dog. Most likely cause?
Pituitary‑dependent hyperadrenocorticism
210
Dog receiving chronic prednisone with PU/PD and ALP elevation. ACTH stim shows flat cortisol. Diagnosis?
Iatrogenic Cushing’s
211
Best test to diagnose iatrogenic Cushing’s.
ACTH stimulation test
212
Most common cause of naturally occurring Cushing’s in dogs.
Pituitary adenoma
213
Most common biochemical abnormality in canine Cushing’s.
Marked ALP elevation
214
ACTH stim: baseline cortisol 3 µg/dL, post ACTH 28 µg/dL. Diagnosis?
Hyperadrenocorticism
215
ACTH stim: baseline cortisol 0.8 µg/dL, post ACTH 0.9 µg/dL. Diagnosis?
Addison’s disease
216
ACTH stim: baseline 1 µg/dL, post ACTH 8 µg/dL in sick dog. Interpretation?
Normal response
217
ACTH stim exaggerated cortisol response indicates what disease?
Cushing’s disease
218
ACTH stim flat response indicates what disease?
Addison’s disease
219
Young dog with vomiting, diarrhea, collapse, Na 122, K 6.8. Diagnosis?
Addison’s disease
220
Dog with Na:K ratio of 17. Most likely endocrine disease?
Addison’s disease
221
Dog with vomiting and weakness but normal electrolytes. Baseline cortisol 0.9 µg/dL. Next test?
ACTH stimulation test
222
Baseline cortisol >2 µg/dL rules out what disease?
Addison’s disease
223
Dog with Addisonian crisis. First treatment step?
IV fluid therapy
224
Why dexamethasone is used initially in suspected Addisonian crisis.
Does not interfere with cortisol assay
225
Mineralocorticoid replacement used in canine Addison’s.
DOCP (desoxycorticosterone pivalate)
226
Maintenance glucocorticoid therapy for Addison’s.
Prednisone
227
Hyponatremia + hyperkalemia + bradycardia. Diagnosis?
Addison’s disease
228
Hypokalemia + hypertension in cat. Diagnosis?
Primary hyperaldosteronism
229
Hyperglycemia + insulin resistance + PU/PD dog. Endocrine cause?
Cushing’s disease
230
Hypoglycemia + weakness in Addisonian dog caused by lack of what hormone?
Cortisol
231
Older cat with hypokalemia, hypertension, ventroflexion of neck. Diagnosis?
Primary hyperaldosteronism
232
Most common adrenal disease diagnosed in cats.
Hyperaldosteronism
233
Major electrolyte abnormality in feline hyperaldosteronism.
Hypokalemia
234
Typical ocular sign in feline hyperaldosteronism.
Retinal hemorrhage from hypertension
235
Treatment of unilateral aldosterone‑secreting adrenal tumor.
Adrenalectomy
236
Medical therapy for hyperaldosteronism when surgery not possible.
Spironolactone
237
Dog with episodic collapse, tachycardia, hypertension and adrenal mass. Diagnosis?
Pheochromocytoma
238
Catecholamine metabolites measured to diagnose pheochromocytoma.
Metanephrine and normetanephrine
239
Most common clinical pattern in pheochromocytoma.
Episodic signs
240
Drug given before pheochromocytoma surgery to prevent hypertensive crisis.
Phenoxybenzamine
241
Pheochromocytomas arise from which adrenal cells?
Chromaffin cells of adrenal medulla
242
Adrenal mass found incidentally during ultrasound called what?
Adrenal incidentaloma
243
Adrenal mass >2 cm is concerning for what?
Malignancy
244
Three diseases to rule out with adrenal incidentaloma.
Cushing’s, pheochromocytoma, hyperaldosteronism
245
Best imaging modality to stage adrenal tumors.
CT scan
246
First‑line drug for canine Cushing’s.
Trilostane
247
Mechanism of trilostane.
3‑beta hydroxysteroid dehydrogenase inhibitor
248
Drug that causes selective adrenal cortical necrosis.
Mitotane
249
Mitotane destroys which adrenal zones?
Zona fasciculata and reticularis
250
Drug used to block aldosterone receptor.
Spironolactone
251
Drug used for mineralocorticoid replacement in Addison’s.
DOCP
252
Most common cause of Addison’s disease.
Immune‑mediated adrenal destruction
253
Most common endocrine cause of PU/PD in dogs.
Cushing’s disease
254
From which embryologic structure does the thyroid gland develop?
Gastrointestinal tract near the base of the tongue
255
Where can ectopic thyroid tissue occur?
Anywhere along the migration path from the base of the tongue to the thoracic inlet
256
What is the functional unit of the thyroid gland?
Thyroid follicle
257
What substance fills the center of thyroid follicles?
Colloid
258
What protein is stored in thyroid colloid?
Thyroglobulin
259
Which transporter concentrates iodine in thyroid cells?
Sodium‑iodide symporter
260
Which enzyme is essential for thyroid hormone synthesis?
Thyroid peroxidase
261
What intermediates form during thyroid hormone synthesis?
MIT and DIT
262
Which combination produces T3?
MIT + DIT
263
Which combination produces T4?
DIT + DIT
264
Which thyroid hormone is biologically active?
T3
265
Which thyroid hormone is secreted most by the thyroid gland?
T4
266
What protein carries most thyroid hormone in circulation?
Thyroxine‑binding globulin
267
What percentage of thyroid hormone circulates free?
<1%
268
What happens to T4 once inside cells?
Converted to T3 by deiodinase enzymes
269
What is the major metabolic effect of thyroid hormone?
Increase metabolic rate
270
How do thyroid hormones affect mitochondria?
Increase number and surface area
271
Why do hyperthyroid animals produce excess heat?
Increased Na/K ATPase activity
272
How does thyroid hormone affect systemic vascular resistance?
Decreases resistance via vasodilation
273
What happens to cardiac output in hyperthyroidism?
It increases
274
How does thyroid hormone affect GI motility?
Increases motility
275
What neurologic effect occurs with excess thyroid hormone?
CNS excitability
276
What neurologic effect occurs with thyroid deficiency?
Lethargy and mental dullness
277
Most common cause of canine hypothyroidism?
Lymphocytic thyroiditis
278
What percentage of canine hypothyroidism is primary?
About 95%
279
How much thyroid destruction occurs before clinical hypothyroidism?
About 80%
280
Common breeds predisposed to hypothyroidism?
Golden Retrievers and Dobermans
281
Typical metabolic signs of hypothyroidism?
Lethargy, weight gain, cold intolerance
282
Common dermatologic sign of hypothyroidism?
Endocrine alopecia
283
Common CBC abnormality in hypothyroid dogs?
Non‑regenerative anemia
284
Common chemistry abnormality in hypothyroid dogs?
Hypercholesterolemia
285
Most common screening test for hypothyroidism?
Total T4
286
Best test measuring biologically active thyroid hormone?
Free T4 by equilibrium dialysis
287
Drug of choice for hypothyroidism?
Levothyroxine
288
Most common cause of feline hyperthyroidism?
Thyroid adenoma or nodular hyperplasia
289
What percentage of feline hyperthyroidism is benign?
About 98%
290
Average age of cats with hyperthyroidism?
Around 13 years
291
Classic clinical signs of feline hyperthyroidism?
Weight loss, polyphagia, hyperactivity
292
Common cardiovascular sign in hyperthyroid cats?
Tachycardia
293
Heart disease hyperthyroidism can mimic?
Hypertrophic cardiomyopathy
294
Why do hyperthyroid cats develop PU/PD?
Increased renal blood flow and GFR
295
Most common laboratory abnormality in hyperthyroid cats?
Elevated liver enzymes
296
Screening test for feline hyperthyroidism?
Total T4
297
Drug of choice for medical treatment of feline hyperthyroidism?
Methimazole
298
Mechanism of methimazole?
Inhibits thyroid peroxidase
299
Definitive treatment for feline hyperthyroidism?
Radioactive iodine (I‑131)
300
Success rate of radioactive iodine therapy?
Approximately 90–95%
301
Dietary treatment for hyperthyroidism?
Iodine‑restricted diet
302
Which cells produce parathyroid hormone (PTH)?
Chief cells of the parathyroid gland
303
Primary organs targeted by PTH?
Bone, kidney, and gastrointestinal tract
304
Effect of PTH on serum calcium?
Increases calcium
305
Effect of PTH on serum phosphorus?
Decreases phosphorus
306
How does PTH increase calcium in bone?
Stimulates osteoclast activity
307
How does PTH affect renal calcium handling?
Increases calcium reabsorption
308
How does PTH affect phosphorus in the kidney?
Increases phosphorus excretion
309
Which vitamin is activated by PTH in the kidney?
Vitamin D (calcitriol)
310
What is the net effect of calcitriol?
Increased intestinal calcium absorption
311
Which pancreatic cells produce insulin?
Beta cells
312
Which pancreatic cells produce glucagon?
Alpha cells
313
Which pancreatic cells produce somatostatin?
Delta cells
314
Main effect of insulin on blood glucose?
Decreases blood glucose
315
Main effect of glucagon on blood glucose?
Increases blood glucose
316
How does insulin lower blood glucose?
Promotes cellular glucose uptake and storage
317
How does glucagon raise blood glucose?
Stimulates glycogenolysis and gluconeogenesis
318
Major hormone deficiency in diabetes mellitus?
Insulin
319
Most common endocrine pancreatic disease in dogs and cats?
Diabetes mellitus
320
Classic clinical signs of diabetes mellitus?
Polyuria, polydipsia, polyphagia, weight loss
321
Primary treatment for diabetes mellitus in dogs?
Insulin therapy
322
Why do diabetic animals develop PU/PD?
Osmotic diuresis from glucosuria
323
Major acute complication of insulin therapy?
Hypoglycemia
324
Which pancreatic islet cells produce insulin?
Beta cells
325
Which pancreatic islet cells produce glucagon?
Alpha cells
326
Which pancreatic islet cells produce somatostatin?
Delta cells
327
Primary effect of insulin on blood glucose?
Decreases blood glucose by promoting cellular uptake and storage
328
Primary effect of glucagon on blood glucose?
Increases blood glucose through glycogenolysis and gluconeogenesis
329
Why do diabetic patients develop polyuria and polydipsia?
Glucosuria causes osmotic diuresis
330
Classic clinical signs of diabetes mellitus?
Polyuria, polydipsia, polyphagia, and weight loss
331
Major hormone deficiency in most diabetic dogs and cats?
Insulin
332
Diagnosis of clinical diabetes mellitus is based on what triad?
Persistent hyperglycemia, persistent glucosuria, and compatible clinical signs
333
What minimum database is recommended at diagnosis of diabetes in dogs and cats per AAHA?
CBC, chemistry with electrolytes, urinalysis with culture, UPC, triglycerides, blood pressure, and thyroid testing where indicated
334
Why is urine culture recommended in glucosuric diabetic patients?
Urinary tract infection can be present even without an active sediment
335
What test helps distinguish stress hyperglycemia from diabetes in cats?
Fructosamine
336
What does fructosamine reflect?
Average blood glucose over the previous 1–2 weeks
337
Why should hyperthyroidism be considered in older cats with suspected diabetes?
It can mimic or coexist with diabetes mellitus
338
At what blood glucose level does glucosuria typically develop in dogs?
About 200 mg/dL
339
At what blood glucose level does glucosuria typically develop in cats?
About 250–300 mg/dL
340
Important risk factors for diabetes in dogs and cats?
Obesity, pancreatitis, insulin-resistant diseases, diabetogenic medications, and diestrus in female dogs
341
Endocrine diseases that can worsen insulin resistance?
Hyperadrenocorticism, acromegaly, hyperthyroidism, and hypothyroidism
342
What reproductive state can cause transient or permanent diabetes in intact female dogs?
Diestrus
343
What important feline diabetic comorbidity can cause plantigrade stance?
Peripheral neuropathy
344
Main treatment goals in diabetes management?
Reduce or eliminate clinical signs while avoiding hypoglycemia
345
What is the AAHA definition of a controlled diabetic?
Absence of clinical signs and hypoglycemia
346
Is the goal of diabetic management to normalize every blood glucose value?
No; the goal is to keep glucose below the renal threshold as much as possible while avoiding hypoglycemia
347
Why are short periods of mild hyperglycemia acceptable in diabetic management?
Because control is defined clinically and overly aggressive treatment increases hypoglycemia risk
348
AAHA first-choice insulin for most diabetic dogs?
Porcine lente insulin (Vetsulin)
349
Recommended starting dose of Vetsulin in dogs per AAHA?
0.25 U/kg every 12 hours, rounded to the nearest whole unit
350
How should meals be scheduled in diabetic dogs?
Equal-sized meals twice daily at the time of each insulin injection
351
Does naturally acquired canine diabetes commonly go into remission?
No, remission is rare
352
What surgery should be recommended in intact diabetic female dogs?
Ovariohysterectomy
353
Common average insulin dose range for well-controlled diabetic dogs?
About 0.5 U/kg every 12 hours, with a range around 0.2–1.0 U/kg
354
AAHA first-choice insulins for diabetic cats?
Glargine or protamine zinc insulin (PZI)
355
Typical starting dose of glargine in cats per AAHA?
0.25 U/kg every 12 hours if BG < 360 mg/dL and 0.5 U/kg every 12 hours if BG > 360 mg/dL
356
Typical starting dose of PZI in cats?
1–2 units per cat every 12 hours
357
Maximum usual starting dose of insulin in cats?
Do not exceed 2 units per cat every 12 hours at initiation
358
Which insulin types are associated with higher remission rates in cats?
Glargine and detemir
359
When is diabetic remission a reasonable goal?
In cats
360
Which insulin is U-40 porcine zinc insulin suspension?
Vetsulin
361
Which insulin is a U-40 human recombinant protamine zinc insulin?
ProZinc
362
Which insulin is a U-100 long-acting human recombinant insulin commonly used in cats?
Glargine
363
Which insulin is a U-100 long-acting analog that is especially potent in dogs?
Detemir
364
Which insulin is generally not recommended in cats because of short duration?
NPH
365
What special caution applies to detemir in dogs?
Dogs are very sensitive to it and require a lower starting dose
366
Why are compounded insulins generally discouraged?
Variable potency, concentration inconsistency, and potential clinical consequences
367
What are the best overall indicators of diabetic control?
Clinical signs and avoidance of hypoglycemia
368
How often should a blood glucose curve be performed even in well-controlled diabetics per AAHA?
At least every 3 months
369
When else should a blood glucose curve be performed?
After changing insulin type, 7–14 days after a dose change, when clinical signs recur, or when hypoglycemia is suspected
370
Ideal nadir during a blood glucose curve?
About 80–150 mg/dL
371
If blood glucose falls below what value should the insulin dose be reduced?
80 mg/dL
372
Target highest glucose on a curve in dogs?
Close to 200 mg/dL
373
Target highest glucose on a curve in cats?
Close to 300 mg/dL
374
How often should BG usually be measured during a standard curve?
Every 2 hours
375
How often should BG usually be measured during a curve in a cat on glargine?
Every 3–4 hours
376
What should be done if glucose is <150 mg/dL during a curve?
Measure more frequently; AAHA recommends hourly when low values are detected
377
Preferred veterinary glucometer mentioned by AAHA?
AlphaTrak 2
378
Why are home blood glucose curves especially helpful in cats?
They reduce the impact of stress hyperglycemia
379
What newer monitoring device records interstitial glucose every 15 minutes for up to 14 days?
FreeStyle Libre continuous glucose monitor
380
What important caveat applies to low FreeStyle Libre readings?
Confirm low values with a blood glucose meter, especially if clinical hypoglycemia is absent
381
Can urine glucose monitoring replace blood glucose monitoring?
No
382
What can persistently negative urine glucose suggest?
Potential insulin overdose or chronic hypoglycemia
383
What is one of the best uses of fructosamine?
Monitoring trends over time
384
What does a fructosamine below the reference interval suggest?
Chronic hypoglycemia
385
In what circumstance can fructosamine help identify impending feline remission?
When it drops low or trends downward while control improves
386
Primary dietary goal in diabetic cats?
High-protein, low-carbohydrate feeding with weight optimization
387
AAHA-recommended approximate carbohydrate content for diabetic cats?
About 12% metabolizable energy
388
Why are canned foods often preferred in diabetic cats?
Lower carbohydrate content, easier portion control, lower caloric density, and increased water intake
389
Are high-fiber diets typically recommended in diabetic cats?
No
390
Primary dietary goals in diabetic dogs?
Consistent intake, weight optimization, and minimizing postprandial hyperglycemia
391
What type of diet is commonly used in diabetic dogs?
A complete and balanced diet, often with increased soluble and insoluble fiber
392
Recommended weekly weight loss goal for obese diabetic cats?
0.5–2% per week
393
Recommended weekly weight loss goal for obese diabetic dogs?
1–2% per week
394
Which sulfonylurea may be used in some diabetic cats if owners refuse insulin?
Glipizide
395
Should glipizide be used in dogs?
No
396
Why is glipizide generally not preferred for long-term feline diabetic management?
Lower success rate and concern for adverse effects including hepatotoxicity and progression of diabetes
397
What alpha-glucosidase inhibitor can be used adjunctively in dogs or cats?
Acarbose
398
What is the mechanism of acarbose?
Inhibits intestinal glucose absorption and reduces postprandial hyperglycemia
399
Which incretin therapies are discussed in the AAHA guidelines?
Exenatide ER and liraglutide
400
Most dangerous acute complication of insulin therapy?
Hypoglycemia
401
What is the Somogyi phenomenon?
Hypoglycemia-induced rebound hyperglycemia
402
What triggers the Somogyi phenomenon?
A glucose concentration <60 mg/dL or a rapid fall in glucose
403
Which counter-regulatory hormones drive the Somogyi effect?
Cortisol, epinephrine, and glucagon
404
How should insulin dose be adjusted if Somogyi is identified?
Decrease the insulin dose
405
If a diabetic is losing weight despite fewer clinical signs, what should be considered?
Insulin dose may still be inadequate or underlying disease may be present
406
Classic triad of diabetic ketoacidosis?
Hyperglycemia, ketosis, and metabolic acidosis
407
Common precipitating factors for DKA?
Infection, pancreatitis, insulin omission, and concurrent disease
408
Common total CO2 finding in DKA?
Decreased total CO2 due to metabolic acidosis
409
Why are diabetic ketotic patients often hospitalized?
They need aggressive therapy and close monitoring
410
What major electrolyte problem often develops during DKA treatment?
Hypokalemia
411
Why can potassium fall during DKA therapy?
Insulin drives potassium intracellularly and fluids increase urinary losses
412
What drug class do Bexacat and Senvelgo belong to?
SGLT2 inhibitors
413
What is the mechanism of SGLT2 inhibitors in diabetic cats?
They inhibit renal glucose reabsorption, causing glucosuria and lowering blood glucose
414
Which two FDA-approved SGLT2 inhibitors are used for feline diabetes in the US?
Bexacat (bexagliflozin) and Senvelgo (velagliflozin)
415
What type of diabetic cats are candidates for Bexacat or Senvelgo?
Otherwise healthy cats with diabetes mellitus that have not previously been treated with insulin
416
Should Bexacat or Senvelgo be used in cats previously treated with insulin?
No
417
Why are previously insulin-treated cats poor candidates for SGLT2 inhibitors?
They are at increased risk of diabetic ketoacidosis, including euglycemic DKA
418
Generic name of Bexacat?
Bexagliflozin
419
Formulation of Bexacat?
Oral tablet
420
Dosing frequency of Bexacat?
Once daily
421
Major boxed-warning concern with Bexacat?
Diabetic ketoacidosis or euglycemic diabetic ketoacidosis, which can be fatal
422
What should be done if a cat on Bexacat develops DKA or euglycemic DKA?
Discontinue Bexacat and initiate emergency treatment, including insulin
423
Generic name of Senvelgo?
Velagliflozin
424
Formulation of Senvelgo?
Oral solution
425
Standard Senvelgo dose?
1 mg/kg orally once daily
426
Major boxed-warning concern with Senvelgo?
Diabetic ketoacidosis or euglycemic diabetic ketoacidosis
427
Should Senvelgo be started in cats with ketonuria, ketonemia, pancreatitis, anorexia, dehydration, or lethargy at diagnosis?
No
428
What is euglycemic DKA?
Ketoacidosis with normal or only mildly increased blood glucose
429
Why can euglycemic DKA be missed in cats taking SGLT2 inhibitors?
Glucosuria lowers blood glucose, masking the severity of ketosis
430
What clinical signs should raise concern for euglycemic DKA in a cat on Bexacat or Senvelgo?
Lethargy, anorexia, vomiting, diarrhea, weakness, or sudden decreases in appetite or water consumption
431
Do Bexacat and Senvelgo replace the need to monitor ketones and clinical status?
No
432
What emergent diabetic complication became more prominent in veterinary medicine after feline SGLT2 inhibitors were introduced?
Euglycemic diabetic ketoacidosis
433
Newly diagnosed diabetic cat, never treated with insulin, otherwise healthy, owner wants oral option. Two FDA-approved choices?
Bexacat or Senvelgo
434
Diabetic cat previously on insulin, now controlled poorly. Is an SGLT2 inhibitor appropriate?
No
435
Diabetic cat on Senvelgo becomes lethargic and ketotic but glucose is near normal. Most likely diagnosis?
Euglycemic DKA
436
Diabetic dog on insulin has recurrent hyperglycemia after documented nadir <60 mg/dL. Most likely explanation?
Somogyi effect
437
Cat with stress hyperglycemia in hospital but uncertain diabetes status. Most helpful next test?
Fructosamine
438
Dog with persistent PU/PD and glucosuria but inactive urine sediment. Important next step?
Urine culture
439
Best first-choice insulin per AAHA for most diabetic dogs?
Porcine lente insulin (Vetsulin)
440
Best first-choice insulins per AAHA for most diabetic cats?
Glargine or PZI
441
Most important overall endpoint in diabetic management?
Control clinical signs without causing hypoglycemia
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