Parathyroid Glands

Question 1

What is the cell type of interest in the parathyroid glands and what do they do? what are the target tissues?

Answer 1

Chief cells
secrete parathyroid hormone (PTH) in a simple feedback system in response to low blood Ca
target tissues are bone and kidney

Question 2

what disorder do we have to know involving hypo function of the parathyroid gland?

Answer 2

hypoparathyroidism

Question 3

what disorder do we have to know involving hyperfunction of the parathyroid gland?

Answer 3

hyperparathyroidism
- primary (functional parathyroid tumors)
- secondary (renal and nutritional)
- pseudohyperparathyroidism (hypercalcemia of malignancy)

Question 4

what pathophy thing does hypoparathyroidism result in?

Answer 4

subnormal amounts of PTH

Question 5

is hypoparathyroidism common?

Answer 5

nope, it’s infrequent

Question 6

what are some potential causes of hypoparathyroidism?

Answer 6

lymphocytes parathyroiditis
destruction by a primary or metastatic tumor
parathyroid gland atrophy
accidental surgical removal

Question 7

what clin path thing does hypoparathyroidism result in? how does this manifest clinically?

Answer 7

hypocalcemia
restless, ataxic, weak, tremors, tetany, seizure (neuro presentation basically)

Question 8

primary hyperparathyroidism is a result of… what?

Answer 8

functional chief cell neoplasm

Question 9

primary hyperparathyroidism occurs most commonly in what signalment/species?

Answer 9

older dogs

Question 10

what pathophys thing does hyperparathyroidism result in?

Answer 10

excess secretion of PTH

Question 11

what are the consequences of excess PTH?

Answer 11

1. bone lesions from widespread osteoclastic resorption (fibrous osteodystrophy)
2. hypercalcemia

Question 12

how does hypercalcemia manifest clinically?

Answer 12

anorexia, vomiting, diarrhea, depression, PU/PD, muscle weakness, ST mineralization

Question 13

what are the two causes of secondary hyperparathyroidism in broad stokes?

Answer 13

renal & nutritional

Question 14

what are the two renal mechanisms of secondary hyperparathyroidism that we have to know?

Answer 14

excess PTH due to hypocalcemia, which is secondary to hyperphosphatemia

impaired production of active form of Vitamin D

Question 15

what are the 3 nutritional mechanisms of secondary hyperparathyroidism that we have to know? which one is most common?

Answer 15

low calcium
inadequate Vit D
high P –> most common

Question 16

high P in horses causing nutritional secondary hyperparathyroidism is called what colloquially?

Answer 16

Bran Disease or Big Head

Question 17

You get parathyroid glands from a horse that look like this. You’ve ruled out a chief cell tumor. what is going on?

Answer 17

secondary hyperparathyroidism from either renal or nutritional mechanisms. given that this is a horse, I’m guessing nutritional (high P)

Question 18

Pseudohyperparathyroidism is also called… ?

Answer 18

Humeral hypercalcemia of malignancy

Question 19

what is the most common cause of hypercalcemia?

Answer 19

hypercalcemia of malignancy

Question 20

what are the two most common malignancies that cause hypercalcemia of malignancy?

Answer 20

lymphosarcoma and apocrine gland carcinoma of the anal sac

Question 21

what is humeral hypercalcemia of malignancy caused by?

Answer 21

over-production of PTH-related protein (PTHrP) by neoplastic cells

Question 22

which is more common in a functional chief cell neoplasm, carcinomas or adenomas?

Answer 22

adenomas > > carcinomas