SEM 5: SAM 1 > Endocrine 1: Thyroid > Flashcards

Endocrine 1: Thyroid Flashcards

(29 cards)

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1
Q

The concentration of hormones at target tissue depends on the rate of ____________(3)

A
  1. Rate of production and secretion (feedback loops)
  2. Rate of delivery (rate of blood flow)
  3. Rate of degradation and elimination (dependent on half life)
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2
Q

List the actions of TSH

A
  1. Increased iodide uptake
  2. Increases thyroid peroxidase
  3. Stimulates synthesis of thyroglobulin
  4. Determines rate of endocytosis
  5. Increases the proportion of T3
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3
Q

Thyroid hormones affects what other physiological processes?

A
  1. Development
  2. Growth
  3. Metabolism

(Also effects cardiac, CNS, and repro)

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4
Q

How do thyroid hormones affect metabolism?

A
  • Increases metabolic rate
  • Increases oxygenation and heat production
  • Stimulates fat mobilization/ breakdown of fats
  • Enhances insulin-dependent entry of glucose into cells
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5
Q

How do thyroid hormones affect cardiac function?

A

Necessary for contractility, heart rate, and vascular tone

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6
Q

What is the most common cause of HypoT?

A

Immune mediated lymphocytic thyroiditis

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7
Q

A patient with immune mediated lymphocytic thyroiditis tend to show clinical signs when _____% of the thyroid gland is destroyed

A

75%

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8
Q

What cardiac findings can be present in a patient with HypoT?

A
  • Bradycardia
  • Weak apex beat
  • Decreased contractility
  • Small complexes on ECG
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9
Q

Explain the body temperature in patients with HypoT with HyperT

A

HypoT: low body temp
HyperT: high body temp

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10
Q

What ocular changes can be seen in patients with HypoT?

A
  • Corneal lipidosis
  • Chronic uveitis
  • KCS
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11
Q

List the possible skin changes seen in patients with HypoT

A
  • Bilateral symmetrical, patchy alopecia
  • Rat tail
  • Dry dull hair coat
  • Thick skin
  • Hyperpigmentation
  • Comedones, seborrhea, hyperkeratosis
  • Easily bruised
  • Poor wound healing
  • Myxoedema
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12
Q

What can be seen on CBC, Chem, and UA that can help lead to diagnosis of HypoT?

A
  • Mild normochromic, normocytic anemia
  • Hypercholesterolemia
  • Low T4
  • May be isosthenuric
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13
Q

List causes of low TT4

A
  1. HypoT
  2. Euthyroid sick syndrome
  3. Drugs (glucocorticoids, anti-convulsants)
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14
Q

What is the pathophysiology behind euthyroid sick syndrome causing low T3/T4?

A

When the body is sick it decreases synthesis of T3/T4 to try and preserve body weight and metabolic demand

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15
Q

T4: LOW
T3: LOW
FT4: LOW
TSH: normal

Primary or secondary HypoT?

A

Secondary HypoT - problem @ the pituitary.. not secreting TSH

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16
Q

T4: LOW
T3: LOW
FT4: LOW
TSH: HIGH

Primary or secondary HypoT?

Study These Flashcards
A

Primary HypoT - @ the level of the thyroid gland… can’t respond to TSH

17
Q

What can a thyroid gland biopsy determine?

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A
  • Differentiates between lymphocytic vs idiopathic atrophy
  • Used to diagnose neoplasia
18
Q

DOC for treatment of HypoT?

Study These Flashcards
A

Levothyroxine (exogenous T4)

19
Q

Congenital HypoT is more common in _________ (dogs/cats)

Study These Flashcards
A

Cats (rare tho)

20
Q

DOC for treatment of HyperT?

Study These Flashcards
A
  • Methimazole
  • Carbimazole
21
Q

What are some disadvantages to treatment of HyperT with drug therapy?

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A
  • Have to have frequent bloodwork rechecks
  • Delayed hypersensitivity in 25% of cats (facial itching, vomiting, liver failure, abnormal blood levels, bleeding)
  • Tumor continues to grow and may become malignant
  • 100% chance of relapse when off meds (life-long drug)
22
Q

How does methimazole work to lower T4 in hyperthyroid patients?

Study These Flashcards
A

Blocks thyroid peroxidase, can’t convert to T3/T4

23
Q

What are some disadvantages to treatment of HyperT with surgical intervention?

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A
  • GA risky in cat with compromised CVS
  • May damage the parathyroid gland causing hypocalcemia
  • Requires hospitalization
  • Voice/purr may change
24
Q

What are some disadvantages to treatment of HyperT with I131?

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A
  • Requires hospitalization
  • Owner has to collect wastes for 2 weeks due to radiation
  • Owner can’t cuddle cat for 2 weeks bc radiation
  • Irreversible process
25
What are some advantages to treatment of HyperT with I131?
- 95% cure rate - Serious side effects are rare - Limited testing needed after tx - Minimal risk of permanent HypoT
26
Which value can be low on CBC/Chem in some patients post-thyroidectomy?
Calcium **(Hypocalcemia post thyroidectomy can occur from damage to the parathyroid gland)**
27
A golden retriever presents with bilateral, non-pruritic alopecia and a rat tail. What tests would you want to run?
T4 and TSH to check for HypoT
28
What condition is associated with disproportionate dwarfism in cats?
Congenital hypothyroidism
29
True or False: patients with Hypothyroidism usually have pruritic skin
False, non pruritic alopecia
SEM 5: SAM 1
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