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Placenta

Hormones


Reviewers: Mandolin Ziadie, M.D. (see Reviewers page)
Revised: 10 October 2011, last major update August 2011
Copyright: (c) 2003-2011, PathologyOutlines.com, Inc.

Definition
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Steroid Hormones: Estrogens and Progesterone
● Trophoblasts synthesize estrogens and syncytiotrophoblasts synthesize progesterone, which maintains a non-contractile uterus and fosters development of an endometrium conducive to pregnancy
● By the end of the first trimester, placental production of these hormones replaces the corpus luteum

Peptide Hormones
Activin and inhibin:
● Produced by trophoblast
● Regulate hCG production

Cytokine Growth Factors (TGF-alpha, TGF-beta, EGF):
● Produced by trophoblast
● Stimulates proliferation of trophoblast and production of fibronectin

Human chorionic adrenocorticotropin (hACTH):
● Small amounts produced
● Believed to function similar to ACTH

Human chorionic gonadotropin (hCG) :
● Glycoprotein similar in structure to pituitary LH
● Synthesized primarily by the villous syncytiotrophoblast
● Synthesis begins before implantation and is detectable 710 days after implantation, forming the basis for early pregnancy tests
● Peak levels reached at 8-10 weeks
● Maintains maternal corpus luteum that secretes progesterone and estrogens

Human chorionic thyrotropin (hCT):
● Small amounts produced, probably by the syncytiotrophoblast
● Believed to function similar to TSH

Human placental growth hormone:
● Differs from pituitary growth hormone by 13 amino acids
● Regulates maternal blood glucose levels so that the fetus has adequate nutrient supply

Human placental lactogen (hPL) :
● Polypeptide similar to growth hormone
● Synthesized by the villous syncytiotrophoblast
● First detectable by 4 weeks
● Peak levels at end of third trimester
● Acts as an insulin antagonist to influence growth, maternal mammary duct proliferation, and lipid and carbohydrate metabolism

Insulin-like growth factors:
● Stimulate proliferation and differentiation of cytotrophoblast

Placental alkaline phosphatase (PLAP):
● Alkaline phosphatase normally produced by syncytiotrophoblast and primordial germ cells
● Also produced in seminoma, intratubular germ cell neoplasia, rarely in other non-germ cell tumors
● May be involved in migration of primordial germ cells in developing fetus

Relaxin:
● Produced by villous cytotrophoblast
● Softens the cervix and pelvic ligaments in preparation for childbirth

SP1:
● Pregnancy specific beta-1 glycoprotein
● Present in syncytiotrophoblast and extravillous trophoblast
● Not in cytotrophoblast

End of Placenta > Hormones


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