Attenuation of the oestrogen positive feedback mechanism with the age in postmenopausal women

ObjectiveIt has been reported that the positive feedback mechanism of oestrogens and progesterone is preserved, although attenuated, in late postmenopausal years. Whether this is also true for the positive feedback effect of oestrogens alone has not been investigated. DesignProspective intervention study. PatientsThirty healthy postmenopausal women. MeasurementsThe women were divided into three groups according to the years since menopause (group I: 2-8years, group II: 9-17years, group III: 18-25years). They were studied during a period of 41days. Two acute experiments (EP) of exogenous oestradiol, given via skin patches, were performed from days 1 to 7 (EP1) and from days 35 to 41 (EP2) to induce an LH surge. Between the two experiments (days 7-34), oestradiol was given at the dose of 100g every 3days, while oral progesterone was added from day 21 to day 34 in order to simulate a luteal phase. Blood samples were taken every 6h during EP1 and EP2 as well as on days 8, 13, 20, 21, 27 and 34. FSH, LH, oestradiol and progesterone were measured in all blood samples. ResultsAn LH surge occurred as a result of the oestradiol positive feedback mechanism in group I and in group II, in both EP1 and EP2. Peak LH values during the surge were significantly lower in group II than in group I in both experiments. None of the patients in group III displayed an LH surge. ConclusionsThese results demonstrate for the first time a gradual attenuation of the pituitary response to oestrogenic provocation over a certain period following the menopause, with complete abolition after 20years. It is suggested that the reserves of pituitary gonadotrophs diminish with age