Granulosa cell aromatase bioassay: Changes of bioactive FSH levels in the female☆

Abstract Some modified forms of follicle-stimulating hormone (FSH) may not cross react with the FSH antibody used in the radioimmunoassay (RIA), but still retain their biological activities. Therefore, estimates of immunoreactive FSH may not correspond with FSH bioactivity. The use of in vitro FSH bioassays may disclose possible roles of these heterogenous forms vivo under various conditions. This review will focus on the history of FSH bioassays, and the widely used in vivo Steelman and Pohley bioassay, based on ovarian weight increase after injection into female rats, is discussed. Since 1971 different biological activities of FSH in various target tissues have been used for the in vitro estimates of FSH bioactivity. The aromatase bioassays involve the measurement of oestradiol in medium of FSH treated Sertoli cells or granulosa cells in culture. Estimates of FSH bioactivity, using the rat granulosa cell bioassay, in serum and urine or normally cycling women, during gonadotropin-releasing hormone-antagonist treatment in hypergonadotropic hypogonadal women and during different stages of female pubertal development will be discussed in more detail.