Plasma levels of immunoreactive parathyroid hormone in dogs chronically exposed to low levels of cadmium chloride.

A previous report had suggested that chronic cadmium intoxication interfered with calcium accumulation in bone and suggested that the mechanism may be a parathyroid-induced bone resorption. We measured C-terminal parathyroid hormone levels in the blood of four male standardized research beagles chronically exposed during 6 months to 25 ppm cadmium chloride in their drinking water while at the same time we performed measurements of the parameters of haversian bone remodelling activity. We failed to demonstrate any statistically significant difference in levels of this hormone in the experimental dogs before or during the exposure, or between samples obtained from the experimental dogs at the end of their period of exposure and normal untreated control dogs from the same colony. We conclude that in the early stages of chronic cadmium intoxication before there is evidence suggestive of intestinal or renal malfunction that may secondarily involve the parathyroid glands, the alteration observed in haversian bone remodelling rates is not mediated through abnormalities of function of the parathyroid glands.