Insulin resistance is more severe in patients with primary hyperparathyroidism

Primary hyperparathyroidism is associated with an increased cardiovascular mortality, and its underlying mechanisms remain unclear. Insulin resistance has been suggested with low level of evidence. The goal of this study was to evaluate glucose metabolism and insulin resistance in primary hyperparathyroidism patients, to compare with control subjects, and to identify risk factors for insulin resistance in patients with primary hyperparathyroidism.

Cross-sectional study of consecutive primary hyperparathyroidism patients without history of diabetes or severe chronic kidney disease (glomerular filtration rate ≤30 mL/min/1.73 m²). Fasting glucose and insulin were evaluated before parathyroidectomy. Glucose metabolism was compared with population-based control subjects (n = 171).

One hundred and seventy-four patients with primary hyperparathyroidism (140 females) were included. Mean fasting glucose was 0.983 ± 0.129 g/L, and 63 patients (36%) had prediabetes (>1.0 g/L). Mean Homeostatic model assessment of insulin resistance (HOMA-IR) was 3.386 ± 3.111 mUI/L, and 78 patients (45%) had insulin resistance (HOMA-IR >2.6). Blood calcium levels (0.171; P = .023) and body mass index (0.450; P < .001) were correlated positively with HOMA-IR. Insulin secretion (HOMA-B%) was correlated positively with preoperative systolic blood pressure in mm Hg (0.187; P = .013). In multivariate analysis, classic hypercalcemic primary hyperparathyroidism (18.47, 6.84-49.87; <.001), mild hypercalcemic primary hyperparathyroidism (5.35, 2.40-11.95; <.001), and body mass index (1.27, 1.17-1.38; <.001) remained independent predictors for insulin resistance (HOMA-IR >2.6). When compared with control subjects, mean HOMA-IR was significantly higher in primary hyperparathyroidism patients (3.386 ± 3.111 vs 1.919 ± 1.158; P < .001).

Insulin resistance was significantly higher in primary hyperparathyroidism patients than in control subjects. The impact of parathyroidectomy on insulin resistance should be evaluated in patients with higher calcium levels.