Immunocytological evidence for parathyroid hormone (PTH) in human fetal parathyroid (PT) glands

Abstract

There is no indication on the stage of fetal development at which the PT cells acquire the ability to synthetize PTH. In order to gain such information, we performed immunocytological studies on PT glands from 29 normal 6 to 24 week-old fetuses obtained after legal abortion, and 1 anenoephalic 35 week-old fetus. Antiserum (GP03) was obtained against bovine PT extracts in guinea-pig ; it cross-reacted with human PTH and was directed against the carboxy-terminal end of PTH. The immunofluorescent reaction was carried out by the indirect method, and its specificity was tested by the usual procedure. No immunoreactive PTH-containing cells were observed in the PT glands of the 6 fetuses younger than 10 weeks, in spite of the fact that organized PT glands were identified by histological method. By contrast, the PT cells gave constantly a fluorescent staining in all fetuses older than 10 weeks of gestation including the anencephalic fetus. All cells were immunoreactive either as a cellular peripheral edging or as a more diffuse cytoplasmic staining around the nucleus. No immunoreactive cells were observed in thyroid or thymic parenchyma. Previous in vitro studies (Soothorne, Ann. N.Y. Acad. Sci., 120 : 669, 1964) suggested that PT function might be active at 12 weeks of gestation. Our data suggest that immunoreactive parathyroid hormone is synthetized by PT gland as early as 10 weeks of gestation, and is present as well in the anencephalic fetus.