Evaluation of a radioimmunoassay for the measurement of amphibian parathyroid hormone. 
A commercial mid-region to carboxyl-region parathyroid hormone (PTH) radioimmunoassay (RIA) for measurement of PTH concentration in serum of humans was evaluated for its ability to detect amphibian PTH.  The recovery of known amounts of human PTH added to aliquots of pooled frog serum demonstrated that frog serum does not interfere with the RIA system.  The mean intraassay coefficient of variation was 0.11.  During the spring and summer removal of the parathyroid glands from frogs resulted in significant decreases in serum calcium levels which the RIA revealed were associated with significant decreases in PTH levels.  In the winter the parathyroid glands of frogs showed histological changes associated with inactivity.  Also, parathyroidectomy of winter frogs did not affect serum calcium concentrations, and PTH levels of experimental and control animals were below or near the level of detection.