The effect of aging on hypothalamic function in oophorectomized women

To detect age-related changes intrinsic to hypothalamic-pituitary function, we studied plasma gonadotropin levels in 12 oophorectomized women ages 27 to 64 years who were not undergoing hormone replacement therapy. Blood drawn from an indwelling catheter every 10 minutes for 5 hours was assayed for follicle-stimulating hormone, luteinizing hormone, estradiol, and prolactin concentrations. All estradiol levels were less than 20 pg/ml and prolactin values were normal. Mean gonadotropin concentrations, pulse frequency, and pulse amplitude were no different in women aged 27 to 49 years as compared with subjects 52 to 64 years old. When grouped according to gynecologic age (years since puberty) or years after oophorectomy, luteinizing hormone and follicle-stimulating hormone mean concentrations, mean pulse frequency, and mean pulse amplitude were comparable to those grouped according to chronologic age. On the basis of our findings, lack of response from postmenopausal ovaries to endogenous gonadotropin stimulation is a result of primary age-related change in the ovary, not in the hypothalamus.