Immunohistochemical demonstration of parathyroid hormone-related protein in thyroid gland of sheep.

Thyroid and parathyroid glands from normal adult sheep and sheep with vitamin D3-induced hypercalcemia were evaluated immunohistochemically for the presence of parathyroid hormone-related protein (PTHrP) and calcitonin (CT). Thyroid follicular cells, C-cells, and parathyroid chief cells stained moderately to strongly positive for PTHrP in both groups of sheep. C-cells were identified as cells positive for cytoplasmic staining of CT. Staining of C-cells for calcitonin in hypercalcemic sheep was diminished in intensity. The data demonstrated that PTHrP is present in the sheep thyroid and parathyroid glands. PTHrP may function as a local paracrine factor in these organs, but its staining intensity was not affected by the induction of hypercalcemia.