The gonadotrophins and their subunits in foetal pituitary glands and circulation

Abstract

Specific radioimmunoassays and column chromatography on Sephadex G-100 have been used to assess the changes in foetal pituitary content and serum concentration of LH, FSH and LH β-subunit and the common α-subunit during gestation. All pituitary glands contained free α-subunit and intact LH. The free α-subunit: LH ratio reached a peak between 10 and 14 weeks of gestation and decreased to adult ratios by term. No FSH was detected in pituitary ( n = 7) extracts from 9.5–12.5 weeks while FSH was detectable in all foetal pituitaries at term. No significant sex difference in intact hormone or subunit concentrations in the pituitary was seen. In contrast to these results the pituitary of an anencephalic foetus (36 week of gestation) contained mainly free α-subunit. During early gestation foetal blood levels of LH-HCG, FSH and free α-subunit were significantly higher than at term. The immunoreactive LH-HCG consisted of both LH presumably from foetal pituitary origin and HCG. These results suggest that during foetal development the first gonadotrophin substance synthetized in the foetal pituitary gland is the common α-subunit. Under hypothalamic influence the synthesis of the β-subunit then takes place leading to the production of the intact gonadotrophins.