Physiology of pregnancy

Question 1

function of hCG

Answer 1

rescue corpus luteum to stimulate luteal estrogen and progesterone secretion until placenta takes over (10 weeks)

Question 2

hCG action

Answer 2

binds to LH receptors, structurally similar to LH, FSH, TSH. May cause transient gestational hyperthyroidism. In males, stimulates Leydig cells (testosterone). Stimulates adrenal fetal cortex.

Question 3

progesterone function

Answer 3

required to maintain quiescent uterus during pregnancy. Decreases uterine contractions, increases secretory activity and fat deposition. Progesterone production independent of fetus. Can’t be used as indicator of fetal health.

Question 4

estrogen production

Answer 4

placenta takes over luteal production of estrogens after 10 weeks. Feto-placental unit responsible for production of: estradiol-17beta, estrone, estriol (need DHEA-S from fetal adrenal gland).

Question 5

estrogen function

Answer 5

Increase: uteroplacental blood flow, uterine smooth muscle hypertrophy, gap junctions, LDL receptor expression on syncitiotrophoblasts, prostaglandins, oxytocin receptors, mammary gland growth, prolactin secretion

Question 6

hPL (hCS) production

Answer 6

produced by syncytiotrophoblasts (proportional to placental weight), levels rise throughout pregnancy

Question 7

hPL actions

Answer 7

antagonizes insulin action (diabetogenicity of pregnancy). Increases glucose availability for fetus. Lypolytic action shifts maternal energy use to FFA. Stimulates mammary gland development.

Question 8

functions of placenta

Answer 8

1. regulate timing and progression of parturition
2. maintain pregnant state of uterus
3. stimulate growth and function of breasts
4. support fetal growth
5. regulate aspects of fetal development

Question 9

PRL release

Answer 9

estrogen promotes PRL release. Lactotroph hypertrophy and hyperplasia increases pituitary size, may cause dizziness, vision problems, vascular insult, and necrosis (Sheehan’s).

Question 10

ADH release

Answer 10

progesterone lowers osmolality threshold for ADH release (ADH is released sooner for a given osmolality)

Question 11

T3/T4 release

Answer 11

Increase in total T3 and T4 in response to hCG (binds TSH receptors). No change in free T3/T4 b/c estrogen promotes liver production of TBG.

Question 12

Cortisol release

Answer 12

Increase in total and free cortisol, despite estrogen-mediated release of CBG.

Question 13

Aldosterone release

Answer 13

increased due to estrogens stimulating hepatic angiotensinogen production and renal renin production. No hypernatremia, hypokalemia, or HTN due to blunting effects of progesterone (competes for same receptors) and lower ADH threshold.

Question 14

prostaglandin actions

Answer 14

1. stimulate myometrial smooth m. contraction
2. promotes gap junction formation btw. uterine smooth m. cells
3. softening, dilation, and thinning of cervix

Question 15

oxytocin function

Answer 15

maintains labor

Question 16

oxytocin release

Answer 16

stimulated by stretch of cervix (Ferguson reflex)