08 - Primary Hyperparathryoidism

Question 1

(E. Primary Hyperparathyroidism)

(BAckground)

1. Parathyroid hormone (PTH) is normally produced in the parathryoid glands by what?
2. secreted in response to what?
3. Physiologic effects of PTH promote what?

(Clinicopathologic features)

1. what age?
2. breed/sex predilection?

Lethargy, hypercalcemia, hyperphosphatemia, increased circulating PTH levels, loss of ability to form concentrated urine leading to polyuria/polydipsia (due to effects of PTH and elevated calcium levels on the renal tubules), and demineralization of bone with proliferation of fibrous tissue and unmineralized osteoid (fibrous osteodystrophy) leading to pathologic fractures (acceleration of osteolytic and osteoclastic bone resorption).

Answer 1

1. the chief cells
2. decreased Ca in the blood
3. increased calcium in the blood (opposed by calcitonin)
4. older dogs or cats
5. no

Question 2

(E. Primary Hyperparathyroidism)

(etiology)

(1. parathyroid (cheif cell) adenomas)
1. how common?
2. result is what?
3. how long to grow?
4. Histologically comprised of compact cords of polyhedral to cuboidal epithelial cells separated by fibrous to fibrovascular septa. Tumors are usually surrounded by a fibrous capsule
5. Clinical signs are related to the inappropriate secretion of PTH by the tumor chief cells.

Answer 2

1. uncommon (but are most common cause in dogs/cats)
2. enlargement of a single parathryoid gland (with atrophy of remaining parathyroids)
3. slow growing

Question 3

(E. Primary Hyperparathyroidism)

(etiology)

(2. Parathyroid (chief cell) carcinomas)
1. rare cause of primary in any species
2. distinction from adenomas relies mainly on envidence of what?
3. may have increased mitotic index and a greater degree of anaplasia, but these features are not completely reliable in distinguishing bening from malignant.

Answer 3

2. invasion into surrounding connective tissues, thyoid gland, and muslce, or evidence of metastasis to regional lymph node/lung

Question 4

(F. Humoral Hypercalcemia of Malignancy (HHM; Pseudohyperparathyroidism)

1. presenting signs and lab findings are very similar to primary although what?
2. What are PTH levels like?

Answer 4

1. hypercalcemia is lower
2. may be within normal range (related to abnormal regulation and episodic release of hormones from tumors) or low in patients with HHM (parathyroids atrophy as a response to persistent hypercalcemia).

Question 5

(F. Humoral Hypercalcemia of Malignancy (HHM; Pseudohyperparathyroidism)

(Etiology)

1. Associated with many different (usually malignant) neoplasms
2. Most often due to secretion of what which binds to what?
3. There are 3 primary mechanisms by which humoral factors can induce hypercalcemia… name them
4. Other humoral effectors of pseudohyperparathyroidism include interleukin-1 (IL-1) and transforming growth factors alpha and beta (TGF-α and TGF-β).

Answer 5

2. parathyroid hormone-related protein (PTHrP) which binds to the N-terminal PTH receptor in bone and kidney
3. stimulation of osteoclastic bone resorption

increase in calcium resorption from kidney

increase in calcium reabsorption from the intestines (less defined in domestic animals)

Question 6

(F. Humoral Hypercalcemia of Malignancy (HHM; Pseudohyperparathyroidism)

(Tumors associated with pseudohyperparathyroidism)

(Dog - Aprocrine adenocarcinoma of the anal sac)

2. malignant?
3. about what percent metastasize to regional lymph nodes?

(Dog - lymphoma)

1. common in what type?
2. account for what % of HHM
3. usually what type of lymphoma?
4. typically involved with increased circulating what?

(Dog - other neoplasms, various carcinomas, myelomas (malignant plasma cell tumors and leiomyosarcomas)

Answer 6

2. highly (invade connectiv tissues and muscle surrounding the anal gland/sac)
3. 95% (iliac and/or lumbar lymph nodes)
4. older, larger breed dogs
5. 20-40%
6. T-cell
7. PTHrP (but levels are lower than in apocrine gland carcinomas suggesting that IL-1 and/or TGFs are also involved)

Question 7

(F. Humoral Hypercalcemia of Malignancy (HHM; Pseudohyperparathyroidism)

(Tumors associated with pseudohyperparathyroidism)

(Horses)

1. what type do you see?
2. mainly those that develop where?

May also see hypercalcemia induced by metastases of solid tumors to bone (less common than in humans) and also associated with hematologic malignancies (eg: leukemias and lymphoma).

Answer 7

1. squamous cell carinomas
2. the esophageal portion of the equine stomach