Placenta as an endocrine organ

Placenta as an endocrine organ

Dr. Sadaf Mumtaz11-2-11

• Placenta – is fetal lung – is also the route by which all nutritive materials enters the fetus– Fetal wastes are discharged to the maternal blood

Placenta is a unique endocrine organ

• Transient tissue• Secretion of its hormone is not subject to

extrinsic control

hCG• Gonadotrophin secreted by placenta• Prolongs life span of corpus luteum

– Estrogen, progesterone and relaxin• Glycoprotein • Produced by syncytiotrophoblast• Two subunits – α and β

– α subunit of LH, FSH and TSH

• Primarily luteinizing and luteotrophic and has little FSH activity• Appears to act on the same receptor as LH• Detected in

– Blood 6days

– Urine 14 days

Rates of secretion of estrogen and progesterone and concentration of hCG at different stages of pregnancy

• In a male fetus…..Role of hCG

• Any role of hCG in inducing vomiting….

• Can ovariectomy before 6th week leads to abortion?

• Why does’nt the developing placenta start producing estrogen and progesterone in the first place instead of secreting hCG?

Secretion of estrogen and progesterone by placenta

Measurement of estriol levels in maternal urine can be used clinically to assess the viability of fetus

Roles of estrogen and progesterone during Pregnancy

• Myometrium

• Breast

• Pelvic ligaments

Role of high estrogen levels

• Gap Junctions

• Increased number of oxytocin receptors

• Cervical ripening local prostaglandins cervical enzymes collagen fibers

Human chorionic Somatomammotropin

• Secreted by syncytiotrophoblast at about fifth week• Lactogenic and growth stimulating activity• CGP [chorionic growth hormone prolactin] or human

placental lactogen (hPL) • Secretion of growth hormone is decreased by hCS• Less potent (potency is a measure of hormone activity expressed in terms of the

amount required to produce an effect of given intensity) • Decreased insulin sensitivity and glucose utilization in

mother sparing it for the fetus• Mobilizes FFA from the mother

• Low hCS levels indicate placental insufficiency

Role of corticotropin releasing hormone

Other Placental hormones

• POMC• GnRH and inhibin-------- regulate hCG• Leptin (Trophoblast and amnion cells)• Prorenin (Cytotrophoblast and amniotic fluid)• Relaxin

– Helps maintain pregnancy by inhibiting myometrial contractions

– Softens the cervix at the time of delivery• Human chorionic thyrotropin

Diffusion of Oxygen

• Diffusion of Carbon dioxide• Diffusion of Food stuff

– Facilitated diffusion of glucose

• Excretion of waste products

• A shift of oxygen Hb dissociation curve to the right in response to increase in blood CO2 and H+ ions has a significant effect by enhancing the release of oxygen from the blood in the tissues and enhancing oxgenation of blood in the lungs. Bohrs effect

Thanks