Reduced insulin sensitivity in adults with pseudohypoparathyroidism type 1a.

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.