Placenta
General
Hormones

Author: Mandolin Ziadie, M.D. (see Authors page)

Revised: 11 October 2017, last major update August 2011

Copyright: (c) 2002-2017, PathologyOutlines.com, Inc.

PubMed Search: Hormones[title] placenta[title]

Table of Contents
Definition / general
Cite this page: Ziadie, M. Hormones. PathologyOutlines.com website. http://pathologyoutlines.com/topic/placentahormones.html. Accessed November 22nd, 2017.
Definition / general
Steroid hormones: estrogens and progesterone
  • Trophoblasts synthesize estrogens and syncytiotrophoblasts synthesize progesterone, which maintains a noncontractile 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 7 - 10 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