Mechanism of renal calcium conservation with estrogen replacement therapy in women in early postmenopause--a clinical research center study

W. Roland McKane, Sundeep Khosla, Mary F. Burritt, Pai C. Kao, David M. Wilson, Steven J. Ory, B. Lawrence Riggs

Research output: Contribution to journalArticlepeer-review

105 Scopus citations

Abstract

To assess the mechanism by which estrogen replacement therapy (EKT) enhances renal calcium conservation in perimenopausal women, we studied 18 normal women in early postmenopause before and after 6 months of ERT (cyclic treatment with transdermal estradiol at 100 μg/day and medroxyprogesterone acetate at 10 mg/day for the first 12 days of each cycle). ITie changes after ERT were: serum ionized calcium and ultrafiltrable calcium, no change; serum intact PTH, 38.2% increase (P < 0.0001); serum 1,25-dihydroxyvitamin D, 23.8% increase (P < 0.0001); urinary calcium excretion, 33.3% decrease (P < 0.001); and deoxypyridinoline (a marker for bone resorption), 19.5% decrease (P < 0.0001). Also, ERT increased tubular reabsorption of calcium (TRCa; 97.6% ± 0.2% to 98.7% ± 0.1%; P < 0.0001), and this increase correlated with that in serum PTH (r = 0.49; P < 0.05). After the infusion of human Kl'H-(1-34), the TRCa maximum was greater after ERT than at baseline (99.4% ± 0.1% vs. 99.0% ± 0.1%; P < 0.0001), resulting in decreased calcium excretion (0.9 ± 0.20 vs. 1.43 ± 0.20 ¿imol/dL glomerular filtrate; P < 0.001). Thus, in early postmenopause, the major mechanism of increased renal calcium conservation after ERT is an increase in TRCa due to an increase in serum PTH because of estrogen-induced inhibition of bone resorption. However, ERT also may directly increase the TRCa maximum in response to PTH.

Original languageEnglish (US)
Pages (from-to)3458-3464
Number of pages7
JournalJournal of Clinical Endocrinology and Metabolism
Volume80
Issue number12
DOIs
StatePublished - Dec 1995

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Biochemistry
  • Endocrinology
  • Clinical Biochemistry
  • Biochemistry, medical

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