WHEN IS IT SAFE TO SWITCH FROM ORAL-CONTRACEPTIVES TO HORMONAL REPLACEMENT THERAPY

Women may continue to use oral contraceptives (OCs) in to their 40's a nd 50's, but to date no method has been evaluated to ascertain their o varian status, i.e., whether fertility and estrogen production have di minished sufficiently so they could be safely switched to hormonal rep lacement therapy. A group of 12 postmenopausal women who had been, for long periods of time, on a regimen of 3 back-to-back packages (i.e., 63 days on, 7 days off) of low-dose oral contraceptives have been stud ied. Secondly, a group of 9 perimenopausal women aged 36 to 47 were ex amined in the same manner. The third group consisted of early reproduc tive age women (arbitrarily divided into subsets aged 17-25 and 26-35 using low-dose OCs in the customary regimen) as normal controls. Bloo d samples were obtained on the last day of a pill cycle and at 7 days off the pill. In some menopausal women, blood samples were obtained at both 7 and 14 days off OCs. Serum was assayed by RIA for estradiol, F SN and LH. As expected in the young reproductive age women, estradiol levels increase at one week off the pill, together with a rebound in F SH and LH to follicular phase levels. In the perimenopausal group, the re was a sharp distinction based on age. The women over 40 showed a mo re marked rise in FSH while those aged 36-40 showed a distinctly lesse r response. Estradiol levels were variable, but tended to show some ag e grouping. Little diagnostic separation was observed for LH. In postm enopausal women, FSH levels were not always elevated at one week post- pill, and even in a second trial with sampling at one and two weeks of f the OC, not all postmenopausal women showed a ''menopausal'' increas e in FSH. The more uniform feature was that estradiol levels never inc reased above basal values. The study found that serum estradiol levels increase after a week off the pill in controls, but are unchanged at one and two weeks in the menopausal group. FSH levels rebound normally in reproductive age women and usually, but not always, increase subst antially in postmenopausal women. After two weeks off OCs, an increase d FSH andlor no change in basal estradiol levels is strong evidence th at it is now safe (contraceptively speaking) to switch from OCs to sta ndard hormone replacement regimens.