Reduced insulin sensitivity in adults with pseudohypoparathyroidism type 1a

Abstract

Context: Disruption of the Gsα maternal allele leads to severe obesity and insulin resistance in mice and early-onset obesity in patients with pseudohypoparathyroidism (PHP) type 1a. However, insulin resistance and glucose metabolism have not been systematically characterized in patients with PHP1a.

Objective, design, and setting: In a cross-sectional, case-control study, we examined insulin sensitivity, β-cell function, energy expenditure (EE), and sympathetic nervous system activity in adults with PHP1a.

Study participants: PHP1a patients (n = 8) and healthy control subjects (n = 24) matched for age (41 ± 7 vs 41 ± 7 years [mean ± SD]), gender, and percent body fat.

Methods: Insulin sensitivity (SI), acute insulin response to glucose, and disposition index were assessed during a frequently sampled iv glucose tolerance test. Oral glucose insulin sensitivity (OGIS) was measured during a mixed meal. EE was measured using whole-room indirect calorimetry. Body composition was assessed via dual-energy x-ray absorptiometry and sympathetic nervous system activity by measuring 24-hour urinary catecholamine concentrations.

Results: PHP1a patients were less insulin-sensitive than their matched controls based upon SI and OGIS. Nondiabetic PHP1a patients tended to have a lower SI (P = .09) and reduced OGIS (P = .03). Disposition index, a composite measure of β-cell function, also tended to be lower in patients (P = .07). Total caloric intake, resting EE, total EE, meal-induced thermogenesis, and 24-hour urinary catecholamine concentrations were not significantly different between the groups.

Conclusions: Adults with PHP-1a have reduced insulin sensitivity compared with their matched controls that may contribute to the pathogenesis of glucose intolerance and diabetes in these patients.

Figures

Figure 1.

Insulin sensitivity in adults with PHP1a and matched controls. Insulin sensitivity was measured by FSIVGTT (A) and mixed meal (B). Values shown are unadjusted means ± 95% confidence intervals. P value indicates significance for comparison between PHP1a patients and matched healthy controls using a linear mixed-effects model. Filled symbols represent PHP1a subjects with type 2 diabetes and their respective controls.