Reproduction 5: Pregnancy Flashcards
What is the first hormone secreted by the syncytiorophoblasts?
hCG
Whatdoes hCG bind to, and what does it do?
bind to LH receptors on corpus luteum and keeps it viable (rescues)
What do pregnancy tests detect?
hCG
What other cells does hCG act on?
fetal leydig cells and adrenal cortex
What are the feedback actions of hCG?
negative feedback on maternal HPG axis
What is hPL?
human placental lactogen
What is hPL also called?
hCS- human chorionic somatomammotropin
what other two hormones is hPL like?
GH and prolactin
How is hPL like GH?
counter-regulatory to insulin (anabolic in the fetus, lipolytic in mom)
mobilizes glucose for fetal use
stimulates fetal IGF-1
How is hPL like prolactin?
stimulates mammary gland development
What is the insulin state during pregnancy?
pregnancy is an insulin-resistant state
What is the result of being in an insulin resistant state?
decreased glucose use by mom allows fetal use
lipolysis and proteolysis provides fatty acids for mom and AA for fetus
What is gestational diabetes caused by?
anti-insulin effects of hPL, progesterone, prolactin, and cortisol
What are the functions of the placenta?
supportive: provides nutrients for fetal growth
immune: prevents rejection of fetus by mother
endocrine: synthesizes hormones
What organs does the placenta perform the functions of?
gut: supplies nutrients
lung: gas exchange
kidney: regulates fluid volume and waste disposal
endocrine
What can’t the placenta make on its own?
cholesterol, must get it from mom - can then convert to progesterone
Why is the placenta considered an incomplete endocrine organ?
can’t complete steroid biosynthesis - gets stuck at progesterone
What is unique in steroid biosynthesis in the syncytiotrophoblast?
StAR independent
What are the sources of cortisol to the syncytiotrophoblasts?
mother and fetal adrenal cortex
What is highly upregulated in the syncytiotrophoblasts, and why
11beta-HSD2, converts cortisol to cortisone, protecting the fetus from too much cortisol
What is relaxin?
inhibits myometrial contractions early in pregnancy
relaxes pelvic bones, ligaments, and softens cervix
involved in reversible hypertrophy of heart?
What produces relaxin?
corpus luteum in response to hCG and by the placenta
What is prolactin?
stimulates lactogenic apparatus during pregnancy
What is prolactin from?
not from placenta, but from maternal pituitary
What i prolactin essential for?
mammotrophic effects of estrogen and progesterone
What is significant lactation inhibited by?
high levels of estrogen and progesterone
What are the cardiovascular changes during pregnancy?
increased stroke volume and heart rate resulting in increased CO
catecholamines mediate chronotropic and ionotropic increases
mild cardiomegaly
What is the change in the MAP during pregnancy?
decreases - TPR decreases more than CO increases
What is the change in pulmonary pressures?
stays the same - decrease in volume offset by decrease in resistance
What is the change in venous pressure during pregnancy?
increases
What are the changes in regional blood flow during pregnancy?
uterus receives up to 30% of CO
skin blood flow increases to maintain body temp
kidney blood flow increases and GFR increases
What are the changes in blood during pregnancy?
increase in blood volume - up to 50% during second trimester - mediated by progesterone
plasma and RBC increase with a net decrease in Hct
What are the respiratory changes during pregnancy?
40% reduction in expiratory reserve due to elevation of diaphragm
increase in tidal volume with no increase in frequency
increased tidal volume results in increased alveolar ventilation - functional alkalosis
What are the GI changes during pregnancy?
additional 30g/day of protein required
decreased mobility which increases nutrient absorption but can result in constipation
decreased LES tone resulting in reflux
What are the endocrine changes during pregnancy?
HPG axis suppressed due to high concentrations of placental sex steroids
growth of pituitary lactotrophs and an increase in PRL secretion (GnRH suppression)
Ant. Pituitary increases in size by 30%
What are the metabolic changes during pregnancy?
first half of pregnancy mother is in anabolic state, second half in state of accelerated starvation
anabolic state: normal or increased sensitivity to insulin, increased fat deposition, glycogen stores, breast growth, nutrient stockpiling
accelerated starvation: mediated by hPL, increased plasma glucose and FA levels
What is accelerated starvation?
catabolic state characterized by insulin resistance
What is the first stage of labor?
activation of the uterus
What does activation of the uterus entail?
release from inhibitory actions of progesterone
Ferguson reflex
fetal HPA axis activated - CRH levels peak
What is the ferguson reflex?
stretch of the cervix from the fetus stimulates release of oxytocin
What are the hormones involved in the initiation and maintenance of labor and uterine evacuation?
progesterone, E2, relaxin, cortisol, oxytocin, CRH, prostaglandins, catecholamines
What is the most important hormone relationship in the initiation and maintenance of labor?
decrease in progesterone and an increase in estrogen
Where is oxytocin released from?
posterior pituitary
What does oxytocin binding to its receptor result in?
PLC cascade results in increased IP3, and an increase in Ca which activates calmodulin
increases uterine smooth muscle contractions
How does E2 influence the response to OT?
E2 increases the number of receptors to OT during pregnancy, increasing the potency of OT
uterus insensitive to OT until 29 wks, then gradually increases 200 fold in early labor
What is used to induce labor?
Pitocin - synthetic OT
What is OT important for in lactation?
not important in formation of milk, but rather for the release/ejection of milk
is maternal OT considered the signal that initiates labor?
No! levels do not increase prior to labor, but rather is released in bursts once labor begins, with increased frequency as labor continues
What is the signal that initiates labor?
Decrease in progesterone/E2 ratio leads to increased prostaglandins which results in increased myometrium Ca leading to more forceful contractions
What does OT stimulate release of?
prostaglandins (also stimulates contractions)
What stimulates lactation?
initiated after delivery by decreased progesterone and E2
What sustains milk secretion?
repeated transient hyperprolactinemia
What does suckling do?
stimulates prolactin release
What does prolactin do?
stimulates maternal behavior during pregnancy and after parturition
suppresses reproductive function (inhibits GnRH)
What is the fundamental secretory unit of the breast-alveolus?
contractile myoepithelial cells, adipose cells
What is the colostrum?
first milk produced, contains very little fat
What is essential for continued milk production?
prolactin, cortisol, insulin
What is oxytocin released in response to?
neural input to NTS (mother response to infant crying) via circulation to the breast
What does it mean that prolactin is a lactogenic hormone?
mammogenic effects: breast development
galactogenic effects: milk production
How does the pill work?
Acts on CNS and urogenital tract to inhibit reproductive function
Pituitary and Hypothalamus – prevents LH surge and ovulation
Basal gonadotropin levels are decreased
Ovary - follicular growth is inhibited
Fallopian tube motility is decreased (in vitro observation)
Glandular atrophy in uterine endometrium – why it is good for controlling heavy menstruation
Inhibits implantation of blastocyst
Causes thick cervical mucus – inhibits sperm motility and migration
What does the progestational drug in the pill do?
prevents LH secretion (including LH surge)
What does the estrogenic drug in the pill do?
inhibits FSH release
What are some non-contraceptive benefits to the pill?
Treatment of excessive menstrual bleeding
Protection for pelvic inflammatory disease
Dysmenorrhea
Hormone replacement therapy in postmenopausal women
What are some risks and side effects of the pill?
Contraindicated in heavy smokers over 35 and those with a history of estrogen-dependent breast carcinomas
Hypertension, myocardial infarction, stroke
Blood clots
Depression
Decreased libido
