title: Progestins increase endogenous opioid peptide activity in postmenopausal women.
abstract: To determine the effect of administration of a progestin alone on endogenous opioid peptide activity, we infused naloxone (2 mg/h for 4 h) into seven estrogen-deficient postmenopausal women before and after oral medroxyprogesterone acetate (Provera; 20 mg) daily for 30 days. Baseline serum LH levels were significantly decreased by the Provera therapy [70.3 +/- 6.6 (+/- SE) vs. 27.5 +/- 1.7 mIU/ml; P less than 0.001]. Naloxone infusion before Provera treatment had no effect on serum LH levels. In contrast, after Provera therapy, a significant (P less than 0.001) increase in LH levels toward the pre-Provera baseline occurred with naloxone infusion. These findings suggest that progestins exert their negative feedback effects on LH at least in part through an opioid peptide-mediated mechanism and that progestin treatment alone can reestablish opiatergic control of LH.
authors.forename: R F
authors.initials: RF
authors.lastname: Casper
authors.forename: S
authors.initials: S
authors.lastname: Alapin-Rubillovitz
mesh_terms: D000368:Aged; D004723:Endorphins / Q000502:physiology*; D004958:Estradiol / Q000097:blood / Q000172:deficiency; D004970:Estrone / Q000097:blood / Q000172:deficiency; D005260:Female; D006801:Humans; D007986:Luteinizing Hormone / Q000097:blood; D008525:Medroxyprogesterone / Q000031:analogs & derivatives / Q000494:pharmacology; D017258:Medroxyprogesterone Acetate; D008593:Menopause; D008875:Middle Aged; D009270:Naloxone / Q000494:pharmacology; D011372:Progestins / Q000494:pharmacology*; D011388:Prolactin / Q000097:blood
chemical_list: D004723:Endorphins; D011372:Progestins; D004970:Estrone; D009270:Naloxone; D004958:Estradiol; D011388:Prolactin; D007986:Luteinizing Hormone; D017258:Medroxyprogesterone Acetate; D008525:Medroxyprogesterone