Oestrogen has no short-term effect on intestinal strontium absorption in healthy postmenopausal women

OBJECTIVE Impaired intestinal calcium absorption in postmenopausal women is often indirectly linked to decreased serum 1,25(OH)(2)D or to intestinal r esistance to its action rather than directly to low circulating oestrogen l evels following the menopause, The purpose of this clinical study was to in vestigate the short-term effect of oral 17 beta-oestradiol on intestinal ca lcium absorption, with strontium as a marker. DESIGN AND PATIENTS Twenty-five healthy postmenopausal women participated i n this randomised double blind placebo controlled clinical trial, Twelve wo men received oestradiol therapy (2 mg/day) and thirteen placebo for 2 month s, Fractional strontium absorption (Fc(240)) was assessed at baseline and a fter 2 months of oestradiol/placebo therapy. RESULTS Intestinal strontium absorption (Fc240) was unchanged after treatme nt with 17 beta-oestradiol (10.1 +/- 5.0 vs. 10.2 +/- 3.8 (%)). Serum total calcitriol (1,25(OH)(2) D) was unchanged after treatment with placebo (88 +/- 22 vs. 79 +/- 21 (pmol/l)) but increased after treatment with oestradio l (88 +/- 30 vs, 116 +/- 33 (pmol/l); P < 0.005). Serum vitamin D binding p rotein (DBP) increased after oestradiol but not after placebo treatment. Th e free serum 1,25(OH)(2)D index was calculated. This index did not change a fter oestrogen therapy (1.6 +/- 0.5 vs. 1.8 +/- 0.5). CONCLUSION In healthy postmenopausal women, short-term suppletion with exog enous oral oestrogen did not influence intestinal calcium absorption as mea sured by the strontium absorption test.