Evaluation of Insulin Resistance in Patients with Primary Hyperparathyroidism

Abstract

Increased plasma insulin levels, both in the fasting state and in response to glucose loads have been reported in patients with primary hyperparathyroidism (1). In this study surgical correction of the hyperparathyroidism was associated with a decrease in plasma insulin levels. However, since glucose tolerance in these patients was similar before and after surgery, it appears that a state of insulin resistance coexisted with the hyperparathyroidism. Documentation of these findings would add hyperparathyroidism to the list of pathologic states associated with antagonism to the action of insulin (2). Furthermore, since hyperin-sulinemia and insulin resistance are often associated with hypertriglyceridemia (3), patients with primary hyperparathyroidism might have an increased incidence of elevated plasma triglyceride levels. In order to evaluate these possibilities, we have measured plasma levels of glucose, insulin, triglyceride, and cholesterol, and directly estimated insulin resistance in a group of patients before and after surgical correction of primary hyperparathyroidism.

Methods. Seven subjects with suspected primary hyperparathyroidism were admitted to the Stanford Clinical Research Center. The group included six females and one male, and had a mean age of 43 yr. All patients consumed a weight maintenance liquid formula diet which included 10 mg/ kg/day of calcium. Various studies of calcium metabolism were undertaken after 3 days of dietary stabilization; including serum calcium, phosphorus and parathy-roid hormone level determinations, 24-hr urinary calcium and phosphorus measurements, and hand, skull, and chest X-rays. Other possible causes of hypercalcemia were excluded by appropriate investigation.

On the fifth and sixth days of hospitali-zation, blood was drawn after an overnight fast for measurement of plasma triglyceride and cholesterol levels. On the fifth hospital day, each patient Received an oral glucose load of 40 g/m 2 , and samples for plasma glucose and insulin determination were drawn during the following three hours.