Circulating levels of follistatin from puberty to menopause

Abstract

To determine the changes in circulating levels of follistatin, a binding protein for activin and inhibin, through the reproductive life cycle in women. An open, prospective descriptive study. An academic endocrine research unit. Prepubertal (n = 10), midpubertal (n = 7), and postpubertal (n = 25) (early adolescent) girls, normal cycling adult women (n = 8), postmenopausal women (n = 17), and men (n = 13) were studied. Normal cycling women were given Nal-Glu GnRH antagonist for 3 days in the follicular phase of the cycle. Serum concentrations of follistatin determined in a heterologous RIA. Mean follistatin levels did not change during puberty but were higher in adult and postmenopausal women. Levels of immunoreactive follistatin in men were lower than levels found in normal cycling women and postmenopausal women. Daily immunoreactive follistatin levels during the menstrual cycle remained constant and did not change significantly after ovarian suppression with GnRH antagonist. Because dynamic changes of serum immunoreactive follistatin do not occur during ovarian activation (puberty), suppression, and age-related ovarian failure, the increase in immunoreactive follistatin levels in adult and postmenopausal women may implicate sources of follistatin other than the ovary.