Insulin sensitivity is inversely correlated with plasma intact parathyroid hormone level

Abnormal glucose metabolism and a high prevalence of diabetes have been reported in patients with primary and secondary hyperparathyroidism. We hypothesize that plasma intact parathyroid hormone (iPTH) level is a determinant of either insulin sensitivity or β-cell function. The study included 52 normotensive, healthy subjects with glucose tolerance. Insulin sensitivity and β-cell function were assessed using a hyperglycemic clamp. Fasting plasma iPTH was determined. The relationships between its level and insulin sensitivity index and β-cell function were examined. Insulin sensitivity index was inversely correlated with plasma iPTH level (r2 =.104, P =.020). The first phase insulin response was positively correlated with plasma iPTH level (r2 =.098, P =.023), but no correlation existed with the second phase insulin response. After adjusting for age, gender, ethnicity, and waist-to-hip ratio, plasma iPTH level was an independent determinant of insulin sensitivity index (P =.019). However, no independent relationship between plasma iPTH level and β-cell function (the first phase and second phase insulin response) was found. In normotensive, glucose-tolerant, and healthy subjects, plasma iPTH level accounts for 10.4% of the variation in insulin sensitivity index. For each pg/mL increment in plasma iPTH level, there is a decrease of 0.247 μmol/L/m2/min/pmol/L in insulin sensitivity index. Although the molecular basis of this relationship is not clear, our results indicate that plasma iPTH level is inversely correlated with insulin sensitivity index. Copyright (C) 2000 by W.B. Saunders Company.