Physiology Q&A

Question 1

What enzyme of steroidogenesis does the placenta lack?

Answer 1

17, 18 desmolase (converts progesterone to androgens and estrogens)

Question 2

Function of relaxin

Answer 2

Maternal hormone of pregnancy. Ensures uterine quiescence; relaxes pelvic ligaments; softens cervix

Question 3

Primary estrogen of pregnancy

Answer 3

Estriol, produced by placenta from sulfated, hydroxylated DHEA from fetus

Question 4

Major source of fetal DHEA-S

Answer 4

Fetal adrenal gland

Question 5

Daily folate recommendation during pregnancy

Answer 5

4 mg (take a dedicated supplement to avoid Vit. A toxicity)

Question 6

PTH net effects (2)

Answer 6

Increase plasma Ca++ Decrease plasma Pi

Question 7

PTH effect on bone

Answer 7

Upregulates production of M-CSF by osteoblasts (promotes differentiation of osteoclast precursors); Stimulates production of RANK-lingand, RANKL (promotes maturation of osteoclasts). ALL EFFECTS ON OSTEOCLASTS ARE INDIRECT

Question 8

PTH effect on kidney

Answer 8

Stimulates CYP1α - endcodes 1α-hydroxylase, which converts to active form of Vitamin D

Stimulates calcium channel insertion in apical membrane of distal tubule

(net effect, increase plasma calcium and vitamin D)

Question 9

Primary regulator of PTH secretion?

Answer 9

Plasma [Ca++].

Note exception to general trend! Increasing [Ca], instead of removing an inhibition, actually “turns off” PTH secretion via calcium sensing receptor

Also regulated by Vitamin D - VDR inhibits PTH

Question 10

Vitamin D Targets

Answer 10

Bone: Remodeling: mobilizes calcium by osteoclast activity; increases bone mineralization by increasing plasma calcium

Gut: Increases Ca++ absorption in duodenum. Increases Pi reabsorption in sm intestine

Kidney: