Pathi

Question 1

The parathyroid glands → from

Answer 1

pharyngeal pouches

Question 2

parathyroid glands location

Answer 2

most commonly : in close proximity to the upper and lower poles of each thyroid lobe •

may be found anywhere along the pathway of descent of the pharyngeal
pouches→
the carotid sheath, the thymus, and elsewhere in the anterior mediastinum

Question 3

Parathyroid gland cells

Answer 3

chief cells
oxyphil cells

Question 4

have secretory granules containing
parathyroid hormone (PTH)

Answer 4

chief cells

Question 5

oxyphil cell
Size
Found
Cytoplasm

Answer 5

slightly larger than the chief cells,

either singly or in small clusters
have acidophilic cytoplasm, and
are tightly packed with
mitochondria

Question 6

The activity of the parathyroid glands is controlled by

Answer 6

level of free (ionized) calcium in the blood,( not by by trophic hormones secreted by the
hypothalamus and pituitary)

Question 7

decreased levels of free calcium →stimulate the synthesis and secretion of PTH, which has the following effects on its target tissues, the kidneys and the bones:

Answer 7

Increased renal tubular reabsorption of calcium

Increased urinary phosphate excretion

Increased conversion of vitamin D to its active dihydroxy form in the kidneys

Enhanced osteoclastic activity

Question 8

The net result of these activities is an

Answer 8

increase in the level of free calcium in the blood, which inhibits PTH secretion from chief cells.

Question 9

Increased conversion of vitamin D to its active dihydroxy form in the
kidneys →

Answer 9

augments gastrointestinal calcium absorption

Question 10

Increased urinary phosphate excretion→

Answer 10

lowering serum phosphate levels (since phosphate binds to ionized calcium)

Question 11

Enhanced osteoclastic activity →

Answer 11

bone resorption → releasing ionized calcium,

Question 12

Tumors of the parathyroid glands, unlike thyroid tumors, usually come to attention because of

Answer 12

excessive secretion of PTH, rather than mass effects.

Question 13

Hyperparathyroidism
primary and secondary, and, less commonly, as tertiary hyperparathyroidism

Answer 13

Primary Hyperparathyroidism →
autonomous, spontaneous overproduction of PTH,

secondary and tertiary
secondary phenomena in patients with chronic renal insufficiency

Question 14

The frequency of occurrence of the various parathyroid lesions underlying
primary hyperparathyroidism →
• Adenoma—…
• Primary hyperplasia (diffuse or nodular)—…• Parathyroid carcinoma—..

Answer 14

85% to 95%

5% to 10%

1%

Question 15

Pathogenesis • Abnormalities in two genes are commonly associated with parathyroid tumors:

Answer 15

1. Cyclin D1 gene rearrangements
2. MEN1 mutations

Question 16

Cyclin D1 is

Answer 16

a positive regulator of the cell cycle

Question 17

inversion on chromosome … repositions the cyclin D1 gene →
resides adjacent to …→ drive abnormal expression of .. in ,….cells → which cause …

Answer 17

11

genomic elements that regulate the PTH gene

cyclin D1

PTH-producing
increased proliferation of these cells

Question 18

Approximately ….tumors have mutations in
both copies of the MEN1 tumor suppressor gene

Answer 18

20% to 30% of sporadic parathyroid

Question 19

spectrum of MEN1 mutations in the sporadic tumors is virtually identical to

Answer 19

familial parathyroid adenomas