Topic Completed: 1 August 2011

Minor changes: 15 February 2019

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PubMed Search: Hormones[title] placenta[title]

Mandolin S. Ziadie, M.D.
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Table of Contents
Definition / general
Cite this page: Ziadie MS. Hormones. website. Accessed September 19th, 2020.
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

  • Produced by villous cytotrophoblast
  • Softens the cervix and pelvic ligaments in preparation for childbirth

  • Pregnancy specific beta-1 glycoprotein
  • Present in syncytiotrophoblast and extravillous trophoblast
  • Not in cytotrophoblast
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