Serum gonadotropins and alpha-subunit decline in aging normal postmenopausal women.

In a group of 680 postmenopausal women participating in a population survey we investigated the relationships between serum gonadotropin, alpha-subunit and PRL concentrations and age, body mass index (BMI), and levels of sex hormone-binding globulin, estrogens, and androstenedione. Gonadotropin and alpha-subunit levels were negatively correlated with age, while PRL levels did not decrease with age. Regression means of serum concentrations in women aged 55 to 75 yr, respectively, decreased for LH from 47.1 to 32.4 IU/L, for FSH from 72.1 to 61.6 IU/L, and for alpha-subunit from 2.6 to 1.9 micrograms/L. The ratio of alpha-subunit to LH and FSH decreased with age. These changes may be caused by either a direct effect of aging on pituitary gonadotroph cells or an effect of aging on the hypothalamic regulation of these cells. Serum gonadotropin and alpha-subunit concentrations were negatively correlated with the BMI, but not with circulating estradiol levels. In addition, we found that estrone and estradiol levels were positively correlated with the BMI, while circulating levels of androstenedione and estrone were more important factors, determining estrone and estradiol levels, respectively. In conclusion, in contrast to what has been reported in normal aging men, serum LH, FSH, and alpha-subunit concentrations decrease with age in normal postmenopausal women.