Primary Hyperparathyroidism

Question 1

What’s the role of PTH, PTHrP, Vitamin D, and calcitonin in Ca2+ homeostasis?

Answer 1

• PTH is released in the face of low calcium to increase resorption from bone, absorption from intestines & kidneys (distal convoluted tubule, ascending loop of Henle), activates vitamin D, which increases Ca absorption from the intestines.
• PTHrP has similar actions as PTH, crucial in the fetus. In healthy adults, its virtually undetectable. Normal to low does not exclude the possibility of a neoplastic process, increased is usually associated with malignant cancer
• Calcitonin: role in limiting postprandial hypercalcemia. still a relatively minor role in calcium homeostasis

Question 2

What’s primary hyperparathyroidism?

Answer 2

• uncommon in dogs, rare in cats
• high PTH despite high calcium levels

Question 3

What are the causes of primary hyperparathyroidism?

Answer 3

• adenoma, carcinoma, or adenomatous hyperplasia
• metastasis

Question 4

What’s the most common clinical complaint for primary hyperparathyroidism from owners?

Answer 4

signs related to urolithiasis or UTI

Question 5

How does primary hyperparathyroidism cause PU/PD?

Answer 5

1. calcium antagonizes the effects of vasopressin
2. calcium inhibits tubular uptake of Na and Cl –> further inhibits urine concentration mechanism

Question 6

How dose hypercalcemia lead to GI signs?

Answer 6

• decreased excitability and dysmotility of the intestines = decreased appetite, vomiting, and constipation

Question 7

How does hypercalcemia lead to urolithiasis?

Answer 7

2 types of stones
- less resorption of calcium + increased excretion of phosphorus = calcium phosphate stone
- with increased calcium (oxalate) absorption from the GI, it can also lead to calcium oxalate stone formation

Question 8

Answer 8

Question 9

Which imaging modality is the most useful for investigating a dog suspected of having a PHPT?

Answer 9

ultrasound of the neck
90-95% patients with PHPT will have nodules (need experienced ultrasonographer)

Question 10

What’s the mainstay therapy for pretreatment for hypercalcemia?

Answer 10

Fluid therapy. 0.9% NaCl 5-10ml/kg/h
can add in furosemide once patient is well hydrated
watch for hypokalemia

Question 11

What are some other options to pre-treat the hypercalcemia?

Answer 11

• glucocorticoids (for hypercalcemia of malignancy)
• bisphosphonates
• calcitonin (salmon)
• plicamycin/ mithramycin

Question 12

How many glands are usually enlarged for primary hyperparathyroidism vs. secondary?

Answer 12

1 vs multiple

Question 13

What is the most successful definitive treatment options for primary hyperparathyroidism?

Answer 13

Surgery

Question 14

What are some other options for definitive therapy for primary hyperparathyroidism?

Answer 14

• u/s guided ethanol ablation
• u/s guided heat ablation

Question 15

What are some ECG changes in patients with hypercalcemia?

Answer 15

• ST segment elevation
• QT shortening
• arrhythmia

Question 16

What’s the an emergency, short term treatment for hypocalcemia?

Answer 16

IV calcium gluconate
watch for long-term use - caustic to blood vessels

Question 17

How frequent is feline primary hyperparathyroidism?

Answer 17

rare

Question 18

What’s the treatment of choice for feline primary hyperparathyroidism?

Answer 18

surgery

Question 19

What’s the long term prognosis post surgery for feline primary hyperparathyroidism?

Answer 19

good

Question 20

What’s the prognosis for canine primary hyperparathyroidism?

Answer 20

short to mid-term (<2y) = excellent
long term is also good for all breeds, except Keeshond - recurrence = possible

Question 21

What are the signs associated with hypercalcemia?

Answer 21

-Renal and Urinary Tract Signs
Polyuria
Polydipsia
Urinary incontinence
Stranguria
Pollakuria
Urolithiasis

-Gastrointestinal Signs
Vomiting*
Inappetence
Constipation

-Neuromuscular Signs
Depression
Exercise intolerance
Shivering*
Muscle twitching*
Seizures*

-Other
Dental pain
Difficulty eating
Stiff gait*
Lameness*

Question 22

What are the signs associated with hypocalcemia?

Answer 22

• Signs Associated with Neuromuscular Excitability
  Muscle fasciculations or tremors
  Face rubbing, biting the paws
  Hypersensitivity to external stimuli
  Stiff, stilted gait
  Tetanic seizures
  Respiratory arrest
• Behavioral Changes
  Agitation
  Anxiety
  Vocalization
  Aggression
• Other
  Panting
  Hyperthermia

Question 23

What are some post treatment considerations?

Answer 23

watch for hypocalcemia crisis
- muscle fasciculations, vocalizations, panting, tetany

Question 24

What are some causes of hypophosphatemia?

Answer 24

• Decreased Intestinal Absorption
  Decreased dietary intake
  Malabsorption/steatorrhea
  Vomiting/diarrhea
  Phosphate-binding antacids
  Vitamin D deficiency
• Increased Urinary Excretion
  Primary hyperparathyroidism
  Diabetes mellitus ± ketoacidosis
  Hyperadrenocorticism (naturally occurring/iatrogenic)
  Fanconi syndrome (renal tubular defects)
  Diuretic or bicarbonate administration
  Hypothermia recovery
  Hyperaldosteronism
  Aggressive parenteral fluid administration
  Hypercalcemia of malignancy (early stages)

-Transcellular Shifts
Insulin administration
Parenteral glucose administration
Hyperalimentation
Respiratory alkalosis