Cyto-immunological study of the ontogenesis of the gonadotropic hypothalamo-pituitary axis in the human fetus

Abstract

Using anti-LH-RH immune serum, LH-RH producing neurons were characterized in the hypothalamus from the 13th week of fetal life up to birth. The immunoreactive perikarya are concentrated in mediobasal, premammillary and anterior hypothalamus (lamina terminalis and rostral commissure region) and their axons contribute to the tubero infundibular tract. They terminate close to the blood vessels of the Mantelplexus before and after the apparition of the intra eminential loops (at the 16th week); immunoreactive fibres terminate also around the capillaries of the vascular organ of the lamina terminalis and near ependymal epithelium. In the pituitary, gonadotropic and thyrotropic cells were immunocytologically demonstrated by anti-FSH absorbed with-HCG and LH, and anti-LH, anti-HCG and anti-TSH absorbed or not with α LH. Only α subunits were identified from the 8th to the 12th week. From the 13th week, β TSH subunits appear in the thyrotrophs. From the 15th week, β FSH and β LH subunits responsible for biological activity were revealed in the same gonadotropic cells; the role of the human fetal hypothalamus in the differentiation of gonadotropic cells is discussed.