Response of hamster thyroid light cells to plasma calcium

Light cells in the hamster thyroid gland were examined by electron microscopy and histochemical methods in control, hypercalcemic and hypocalcemic animals. Elevation of plasma calcium levels stimulated a marked depletion of light cell granules as detected by electron microscopy and silver impregnation. In the hypercalcemic state the size and number of light cells did not differ from that of control animals. Hypocalcemic hamsters showed a significant increase in light cell numbers with marked hypertrophy and hyperplasia of this cell type. These observations support the view that the light cell in the hamster thyroid is associated with thyrocalcitonin secretion.