Qualitative difference in follicle-stimulating hormone activity in the pituitaries of young women compared to that of men and elderly women.

The possible existence of qualitative differences between FSH in pituitaries from men and women of different ages was investigated with the use of an in vitro bioassay, an in vitro bioassay, and a RIA. Aqueous extracts were made from pituitaries obtained at autopsy and frozen until extracted. The FSH activities per pituitary and the ratios of FSH activities as obtained with the three assay methods were similar for young and elderly men. The ratios of in vivo biological to in vitro biological FSH activities were similar for men and postmenopausal women and significantly higher than the corresponding ratio for FSH from young women. With the in vivo bioassay the activity in the extracts of pituitaries from men and young women were similar, whereas extracts from postmenopausal women had significantly higher activity. With the in vitro bioassay the extracts from young women and elderly women had a similar content of FSH activity, whereas the FSH level in the extracts of male pituitaries was significantly lower. The results of the RIA correlated well with those of the in vitro bioassay. In conclusion, the results show that FSH in pituitaries from young women has a biological activity that is qualitatively different from FSH of men and elderly women. The relatively low in vivo biological activity of FSH from young women compared to FSH from men and elderly women was most likely due to a more rapid clearance of the hormone from the circulation of the test animal.