Parathyroid Disorders

Question 1

Parathyroid chief cells secrete ___

Answer 1

PTH

Question 2

Parathyroid oxyphil cells are ___ and contain ___

Answer 2

acidophilic; mitochondria

Question 3

How does parathyroid detect changes in ECF calcium?

Answer 3

Decrease ECF calcium ↓ CaSR activity

Question 4

PTH actions on kidney & bone

Answer 4

↑ Ca2+ resorption in kidney/bones (osteoclastic)

↓ PO43- resorption in kidney

vitamin D synthesis in kidney

Question 5

Vitamin D promotes ___

Answer 5

Ca2+ absorption in small intestine (when vit D is converted to active dihydroxy form)

Question 6

Phosphate action on calcium

Answer 6

Binds to calcium (↓ in serum)

Question 7

Role of FGF 23

Answer 7

↓ sodium phosphate cotransporters in kidney PCT (↓ serum phosphate)

↓ 1,24 dihydroxy Vit D

Question 8

RANKL action

Answer 8

Osteoblast protein that interacts with osteoclasts

Question 9

RANK action

Answer 9

receptor on osteoclasts for interaction with osteoblasts

Question 10

Osteoprotegerin action

Answer 10

binds RANKL to ↓ RANKL-RANK activity, ↓ osteoclast activity

Question 11

M-CSF action

Answer 11

proliferation of osteoclast precursor cells

Question 12

Three inducers of RANKL expression

Answer 12

progesterone, PTH, calcitriol (vit D3)

Question 13

___ induces OPG, which ___ osteoclast activity.

Answer 13

Estrogen; decreases

Question 14

1° hyperparathyroidism vs malignant hypercalcemia

Answer 14

1° hyperparathyroidism: ↑ PTH causes ↑ Ca2+

Malignancy: ↑ PTH-like polypeptide ↑ Ca2+

Question 15

Three genetic causes of 1° hyperparathyroidism

Answer 15

1. Cyclin D1 overexpression d/t Chr11p inversion
2. MEN1 or MEN2A mutations
3. Familial hypocalciuric hypercalcemia

Question 16

Pathogenesis of familial hypocalciuric hypercalcemia

Answer 16

AD mutation in CASR ↓ activity

Question 17

Parathyroid adenoma vs parathyroid hyperplasia vs parathyroid carcinoma

Answer 17

Adenoma: solitary nodule in single gland

Hyperplasia: all 4 glands involved - asymmetry

Carcinoma: invasion of surrounding tissues & metastasis

Question 18

Kidney findings in hyperparathyroidism

Answer 18

nephrolithiasis & nephrocalcinosis (calcification)

Question 19

Describe osteitis fibrosa cystica

Answer 19

Bony pain due to cystic bone spaces w/ brown fibrous tissue. Most common in parathyroid carcinoma.

Question 20

Presentation of hyperparathyroidism

Answer 20

“Stones, thrones (polyuria), bones, groans, psychiatric moans”

Question 21

Labs in 1° hyperparathyroidism

Answer 21

↑ Ca2+, ↑ PTH, ↓ serum phosphate, hypercalciuria, hyperphosphaturia

Question 22

2° hyperparathyroidism usually caused by ___.

Answer 22

Renal insufficiency ↓ phosphate excretion (binds Ca2+) & ↓ active Vit D (↓ Ca2+ absorption)

Question 23

Labs in 2° hyperparathyroidism

Answer 23

↓ Ca2+, ↑ serum phosphate, ↑ PTH, ↓ vit D, ↑ ALP

Question 24

Most common causes of hypoparathyroidism

Answer 24

-Direct injury or vascular injury (surgery)
-autoimmune
-DiGeorge (22q11 deletion) - absence of parathyroids

Question 25

Clinical findings in hypoparathyroidism

Answer 25

Chvostek sign: facial twitch when cheek is tapped Trousseau sign: carpopedal spasm with BP cuff

Question 26

Chronic manifestations of hypoparathyroidism include ___.

Answer 26

calcification of basal ganglia

Question 27

Labs in hypoparathyroidism

Answer 27

↓ PTH, ↓ Ca2+, ↑ serum phosphate

Question 28

Pathogenesis of pseudohypoparathyroidism

Answer 28

AD maternal imprinting mutation of GNAS → inactivated cell signaling w/ adenylate cyclase → PTH resistance in renal tubule

Question 29

Clinical features of pseudohypoparathyroidism

Answer 29

Albright hereditary osteodystrophy (short 4th/5th digits, obese, short stature, developmental delay)

Question 30

Labs in pseudohypoparathyroidism

Answer 30

↑ PTH, ↓ Ca2, ↑ serum phosphate