Mechanism of renal calcium conservation with estrogen replacement therapy in women in early postmenopause - A clinical research center study
Article
Mckane, WR, Khosla, S, Burritt, MF et al. (1995). Mechanism of renal calcium conservation with estrogen replacement therapy in women in early postmenopause - A clinical research center study
. JOURNAL OF CLINICAL ENDOCRINOLOGY & METABOLISM, 80(12), 3458-3464. 10.1210/jc.80.12.3458
Mckane, WR, Khosla, S, Burritt, MF et al. (1995). Mechanism of renal calcium conservation with estrogen replacement therapy in women in early postmenopause - A clinical research center study
. JOURNAL OF CLINICAL ENDOCRINOLOGY & METABOLISM, 80(12), 3458-3464. 10.1210/jc.80.12.3458
To assess the mechanism by which estrogen replacement therapy (ERT) 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). The 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 PTH-(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 μmol/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.
