The developments of the adenohypophyses in human fetuses ranging from 40mm to 270mm in crown rump length were observed by fine structural and immunocytochemical studies.
Somatotrophs, corticotrophs and gonadotrophs were first observed at 40mm fetus. Somatotrophs were well differentiated and easily identified at this time. At 210mm fetus, immunostained somatotrophs were spherical in shape and contained dense secretory granules ranging 300~500nm in diameter.
At 100mm fetus, mammotrophs and thyrotrophs were first detected. Mammotrophs were spherical or polygonal in shape and contained the largest granules in all cells in the pars anterior. At 210mm fetus, mammotrophs showed some development of the cytoplasm, which had lamellar endoplasmic reticulum.
Two types of gonadotrophs, luteinizing hormone and follicle stimulating hormone cells, were observed at 40mm and 100mm, respectively. With the increase of fetal age, luteinizing hormone cells showed steady development whereas the follicle stimulating hormone cells exhibited poor development of cytoplasm.
The corticotrophs of 40mm fetus had already characteristic dense core granules. At 100mm fetus, the corticotrophs began to develop rapidly and to increase in quantity. From 210mm fetus, the cytoplasm was filled with variable sized granules, small secretory granules of 150~250nm in diameter and well-developed Golgi apparatus.
Thyrotrophs were relatively well differentiated from 100mm fetus onwards. At 210mm,
immunoreactive thyrotrophs were polygonal or oval with small secretory granules of 150nm in diameter. Their granules were the smallest in all cells in the gland.
The follicular cells were most numerous in the pars anterior of fetal hypophysis. These cells were already well differentiated at term.
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