ABSTRACT
Geometrically increasing doses of cortisone (0.5, 1.5 and 4.5 mg twice daily) were injected into pregnant rats, and the volume, nuclear diameters and mitotic rate of the maternal parathyroids as well as the parathyroid volume and mitotic rate in the foetuses were determined. The nuclear diameters were if anything smaller and the mitotic rate tended to decrease in the cortisone treated groups. There were no significant differences between the parathyroid volumes of the foetuses in the control and cortisone-treated groups. Thus, it seems that the development of the rat foetal parathyroids and the morphology of the maternal parathyroids are little affected if at all, by cortisone.