Rising Glucagon-Like Peptide 1 Concentrations After Parathyroidectomy in Patients With Primary Hyperparathyroidism

Although primary hyperparathyroidism has been associated with insulin resistance, potential optimal effects of parathyroidectomy (PTX) on glucose homeostasis remain controversial. Accordingly, the impact of PTX on glucose-stimulated incretin (glucagon-like peptide 1 [GLP-1] and gastric inhibitory peptide) secretion has not been evaluated. The aim of this pilot study was to compare glucose-stimulated incretin secretion (GSIS) in patients with asymptomatic primary hyperparathyroidism with normal glucose homeostasis, before and after PTX.

Fourteen patients were included in the study. Fasting calcium, parathyroid hormone, glucose, insulin, GLP-1, and gastric inhibitory peptide were measured pre- and post-operatively. Homeostasis Model Assessment 2, QUICKI, and Matsuda indexes were used as markers of insulin sensitivity and resistance before and after PTX. Preoperatively, a 75 g oral glucose tolerance test (OGTT) was performed to evaluate the response of glucose, insulin, and GSIS. OGTT measurements were repeated 6 ± 2 wk post-PTX.

Patients had a mean age of 52.93 ± 9.96 y, and female-to-male ratio was 12:2. Pre- and post-operatively, a positive correlation between parathyroid hormone and Homeostasis Model Assessment 2 for β-cell function was evident (r = 0.74, P = 0.002 and r = 0.55, P = 0.04, respectively). After PTX, a significant increase in GSIS for GLP-1 during OGTT was observed (in 60 min: 63.06 ± 44.78 versus 102.64 ± 40.19 pg/mL, P = 0.02; and in 120 min: 71.20 ± 35.90 versus 102.49 ± 40.02 pg/mL, P = 0.03).

The increase of GLP-1 response following oral glucose load after PTX may reflect an initial recovery phase of glucose homeostasis. Long-term studies are required to elucidate the physiological interplay between the normalization of calciotropic axis and the rising GLP-1 concentrations post-PTX.