A longitudinal study of the perimenopausal transition: altered profiles of steroid and pituitary hormones, SHBG and bone mineral density.

From a longitudinal prospective study, 160 women with spontaneous menopause and without steroid medication were followed during the transition from pre- to postmenopause. After 12 years 152 women were still participating in the study. Blood samples were drawn every 6 months until 1 year after the menopause and every 12 months thereafter. Measurements of bone mineral density (BMD) on the forearm were performed every second year. All women routinely completed a questionnaire concerning symptoms frequently attributed to the climacteric period. All data were grouped around the onset of the menopause, thereby allowing longitudinal evaluation of the changes in the variables from the premenopausal to the postmenopausal period. The beginning of the perimenopausal period was characterized by transitory elevations of follicle-stimulating hormone (FSH). A significant increase in serum levels of gonadotropins was observed for both FSH and luteinizing hormone (LH) from about 5 years before the menopause. Within the 6 month period around the menopause there was a further increase which culminated within the first postmenopausal year for LH and 2-3 years postmenopause for FSH. Thereafter, a continuous decrease in LH occurred over the following 8 years. With respect to FSH, there was a slight decline starting about 4 years postmenopause. During the premenopausal period an increasing frequency of inadequate luteal function or anovulation occurred and, in the postmenopausal years, the serum levels of progesterone (P) were invariably low. Gradually, the ratio between estrone (E1) and 17-beta-estradiol (E2) increased, reflecting the declining follicular steroidogenesis. A marked decrease in estrogen levels occurred during the 6 month period around the menopause, most pronounced in E2. During the next 3 years, the levels of E2 and E1 showed an essentially parallel, moderate decline. Around the menopause, serum levels of testosterone (T), delta4-androstenedione (A) and sex hormone-binding globulin (SHBG) showed small but significant decreases. From about 3 years postmenopause, the levels were relatively constant over the following 5 years. A decrease in BMD was observed in the postmenopause, and from about 3 years postmenopause, estradiol correlated positively with BMD. Before, as well as after the menopause, body mass index (BMI) showed an inverse correlation with SHBG. Postmenopausal androstenedione correlated positively with E1, E2 and T. BMI correlated positively with E1 and E2. The concentrations of the free fraction of E2 and T are dependent on the levels of SHBG, which in turn has a negative correlation with BMI. The impact of this will influence the severity of symptoms, the degree of bone loss and the need for supplementary therapy.