Pathology of Experimental Vitamin D Deficiency Rickets in Growing Chickens. II. Parathyroid Gland

Histopathological studies were done on the enlarged parathyroid glands in experimental vitamin D deficiency rickets of growing broiler chickens ranging from 1 to 7 weeks of age. Two types of parenchymal cells, light and dark chief cells, were recognised in the control group. The former type of cells appeared predominantly in the stages during which bone growth was the most rapid. The main lesions in the groups deficient in vitamin D were swelling and hyperplasia of the parenchymal cells with increased numbers of mitotic figures, a cord-like arrangement of the cells with the formation of surrounding spaces, and a proliferation of the stromal connective tissue. Swelling and hyperplasia of the parenchymal cells, especially the light chief cells, were regarded as the most characteristic changes in hyperparathyroidism and the cord-like arrangement of cells as the second most characteristic alteration.