Pathology 2: Parathyroid Disorders

Question 1

What is the histology of the parathyroid gland?

Answer 1

Composed mostly of chief cells and oxyphil cells within an adipose stroma.

Question 2

What do the chief cells look like on H&E stain?

Answer 2

On H&E staining, the chief cells range from light to dark pink and contain secretory granules of parathyroid hormone (PTH).

Question 3

What do the oxyphil cells look like under the microscope?

Answer 3

Oxyphil cells are slightly larger than the chief cells, have acidophilic cytoplasm, and are tightly packed with mitochondria.

Question 4

What controls the activity of the parathyroid gland?

Answer 4

Controlled by the level of calcium in the bloodstream.

Question 5

How does the parathyroid effect calcium?

Answer 5

They decrease levels of free calcium, and stimulate the synthesis and secretion of PTH.

Question 6

List the 4 effects of PTH?

Answer 6

1- Increase in renal tubular reabsorption of calcium.
2- Increase in urinary phosphate excretion.
3- Increase in the conversion of vitamin D to its active dihydroxy form in the kidneys.
4- Enhancement of osteoclastic activity.

Question 7

What is the net result of the activities of the PTH?

Answer 7

Increase the level of free calcium, which inhibits further PTH secretion.

Question 8

List the 3 forms of hyperthyroidism?

Answer 8

1- Primary hyperthyroidism.
2- Secondary hyperthyroidism.
3- Tertiary hyperthyroidism.

Question 9

Primary hyperthyroidism is a disease of which group?

Answer 9

Disease of adults.

Question 10

Primary hyperthyroidism is more common in which gender?

Answer 10

More common in women.

Question 11

List the 3 types of parathyroid lesions causing hyperfunction?

Answer 11

1- Adenoma 75% to 80%.
2- Primary hyperplasia 10% to 15%.
3- Parathyroid carcinoma 1%.

Question 12

List the 3 genetic syndromes associated with familial primary hyperthyroidism?

Answer 12

1- Multiple endocrine neoplasia - 1 (MEN-1).
2- Multiple endocrine neoplasia - 2 (MEN-2).
3- Familial hypocalciuric hypercalcemia.

Question 13

List the 3 molecular defects that have a role in pathogenesis of sporadic adenomas?

Answer 13

1- Cyclin D1 gene inversions.
2- MEN1 mutations.

Question 14

What is the morphology of parathyroid adenomas?

Answer 14

1- Solitary.
2- Averages 0.5 to 5 gm.
3- well-circumscribed, soft, tan to reddish-brown nodule.
4- Surrounded by delicate capsule.
5- The glands outside the adenoma are usually normal in size or shrunken.
6- It is composed of uniform, polugonal chief cells with small, centrally placed nuclei.
7- A rim of compressed, non-neoplastic parathyroid tissue at the edge of the adenoma.
8- Not uncommon to find bizarre and pleomorphic nuclei.
9- Adipose tissue is inconspicuous.

Question 15

What is the pathogenesis of primary hyperplasia?

Answer 15

It may occur sporadically or as a component of MEN syndrome.

Question 16

How many glands are involved in primary hyperplasia?

Answer 16

All four glands are involved (asymmetry).

Question 17

What is the most common microscopic pattern in primary hyperplasia?

Answer 17

The most common microscopic pattern is that of chief cell hyperplasia (diffuse or multinodular).

Question 18

What other microscopic findings are found in primary hyperplasia?

Answer 18

Stromal fat is not easily seen.

Question 19

Parathyroid carcinomas usually enlarge how many glands?

Answer 19

One parathyroid gland.

Question 20

What is the gross findings in parathyroid carcinomas?

Answer 20

Consists of gray-white, irregular masses that sometimes are >10 gm in weight.

Question 21

What is the microscopic findings in parathyroid carcinomas?

Answer 21

Usually uniform, arranged in nodular or trabecular patterns, with a dense fibrous capsule.

Question 22

A diagnosis of parathyroid carcinoma is based on what?

Answer 22

1- Invasion of surrounding tissues.
2- Metastasis.

Question 23

What are the morphologic skeletal changes found in parathyroid carcinoma?

Answer 23

1- Osteoporosis:
- Osteitis fibrosa cystica:
- bone contains widely spaced, delicate trabeuclae.
- the cortex is thinned.
- the marrow contains ( a lot ) of fibrous tissue.
- there are foci of hemorrhage and cyst formation.

• Brown tumors:
  
  • aggregates of osteoclasts, reactive giant cells, and hemorrhagic debris from masses.

Question 24

What other morphologic changes in other organs are found in parathyroid carcinoma?

Answer 24

PTH-induced hypercalcemia favors the formation of urinary tract stones (nephrolithiasis) as well as calcification of the renal interstitial and tubules (nephrocalcinosis).

Question 25

Metastatic calcification secondary to hypercalcemia also may be seen in which other sites?

Answer 25

Stomach, lungs, myocardium, and blood vessels.

Question 26

What is the most common sign of primary hyperparathyroidism?

Answer 26

It is asymptomatic.
Hypercalcemia.

Question 27

What are the labrotory investigation and findings for asymptomatic primary hyperparathyroidism?

Answer 27

1- Serum PTH levels are inappropriately elevated for the level of serum calcium.
2- Hypophosphatemia.
3- High urinary excretion of both calcium and phosphate.

Question 28

The signs and symptoms of symptomatic primary hyperparathyroidism reflect the combined effect of ________ and _______?

Answer 28

Combined effects of high PTH secretion and hypercalcemia.

Question 29

List 6 signs and symptoms of symptomatic primary hyperparathyroidism?

Answer 29

1- Bone pain.
2- Renal stones.
3- Chronic renal insufficiency (polyuria and secondary polydipsia).
4- Constipation, nausea, peptic ulcers, pancreatitis, gallstones.
5- Depression, lethargy and seizures.
6- Aortic or mitral valve calcifications.

Question 30

Secondary hyperparathyroidism is caused by what?

Answer 30

Caused by any condition that gives rise to CHRONIC hypocalcemia.

Question 31

What is the most common cause of secondary hyperparathyroidism?

Answer 31

Renal faliure:
- hyperphosphatemia.
- loss of renal substance > low active form of vitamin D.

Question 32

What is the morphology of secondary hyperparathyroidism?

Answer 32

1- The parathyroid glands:
- hyperplastic.
- contains an increase number of chief cells, or cells with more abundant clear cytoplasm.

2- Fat cells are decreased in number.
3- Bone changes.
4- Metastatic clarification may be seen in many tissues.

Question 33

What is the clinical course of secondary hyperparayhroidism?

Answer 33

• The clinical features are overlooked by symptoms of chronic renal failure.
• Changes are less severe than are those seen in primary hyperparathyroidism.
• The vascular calcification may result in ischemic damage.
• Serum calcium remains near normal.

Question 34

What is tertiary hyperparathyroidism?

Answer 34

A state of autonomous excessive secretion of parathyroid hormone (PTH) after a long period of secondary hyperparathyroidism and resulting in a high blood calcium level.

Question 35

What is hypoparathyroidism?

Answer 35

An absolute reduction in secretion of PTH leading to to hypocalcemia.

Question 36

List the 5 etiologies of hypoparathyroidism?

Answer 36

1- Surgically induced hypoparathyroidism (most common cause).
2- Autoimmune hypoparathyroidism.
3- Autosomal-dominant hypoparathyroidism.
4- Familial isolated hypoparathyroidism (FIH).
5- Congenital absence of parathyroid glands (such as DiGeorge syndrome).

Question 37

What is the laboratory findings in hypoparathyroidism?

Answer 37

Low serum PTH.
Low serum calcium.
High levels of phosphate.

Question 38

List 6 clinical manifestations of hypoparathyroidism?

Answer 38

1- Tetany.
2- Mental status changes.
3- Intracranial manifestations.
4- Ocular disease.
5- Cardiovascular manifestations.
6- Dental abnormalities.

Question 39

Which condition has high PTH, high calcium, and low phosphate?

Answer 39

Primary hyperparathyroidism.

Question 40

Which condition has high PTH, low calcium, and high phosphate?

Answer 40

Secondary hyperparathyroidism.

Question 41

Which condition has low PTH, low calcium, and high phosphate?

Answer 41

Primary hypoparathyroidism.