Objective: Parathyroid hormone (PTH) is a key hormone in regulation of calcium homeostasis and its secretion is regulated by calcium. Secretion of PTH is attenuated during intake of nutrients, but the underlying mechanism(s) are unknown. We hypothesized that insulin acts as an acute regulator of PTH secretion.
Methods: Intact PTH was measured in plasma from patients with T1D and matched healthy individuals employing 4-hour oral glucose tolerance test (OGTT) and isoglycemic intravenous glucose infusion on two separate experimental. In addition, expression of insulin receptors on archived, surgical specimens of parathyroid glands were assessed by immunochemistry (IHC) and quantitative polymerase chain reaction (qPCR).
Results: The inhibition of PTH secretion was more pronounced in healthy individuals compared to patients with T1D during an OGTT (decrementalAUC0-240min: -5256 ± 3954 min×ng/L and -2408 ± 1435 min×ng/L, P=0.030). Insulin levels correlated significantly and inversely with PTH levels, also after adjusting for levels of several gut hormones and BMI (P=0.002). Expression of insulin receptors in human parathyroid gland were detected by IHC and qPCR.
Conclusion: Our study suggests that insulin may act as an acute regulator of PTH secretion in humans.