Context and Objective: Metabolic and body compositional consequences of GH deficiency (GHD) in adults are associated with a phenotype similar to the metabolic syndrome (MetS).

Patients: We assessed MetS prevalence in adult GHD patients (n = 2531) enrolled in the Hypopituitary Control and Complications Study. Prevalence was assessed at baseline and after 3 yr of GH replacement in a subset of 346 adult-onset patients.

Results: Baseline MetS crude prevalence was 42.3%; age-adjusted prevalence in the United States and Europe was 51.8 and 28.6% (P < 0.001), respectively. In the United States, age-adjusted prevalence was significantly higher (P < 0.001) than in a general population survey. Increased MetS risk at baseline was observed for age 40 yr or older (adjusted relative risk 1.34, 95% confidence interval 1.17–1.53, P < 0.001), females (1.15, 1.05–1.25, P = 0.002), and adult onset (1.77, 1.44–2.18, P < 0.001). In GH-treated adult-onset patients, MetS prevalence was not changed after 3 yr (42.5–45.7%, P = 0.172), but significant changes were seen for waist circumference (62.1–56.9%, P = 0.008), fasting glucose (26.0–32.4%, P < 0.001), and blood pressure (59.8–69.7%, P < 0.001). Significantly increased risk of MetS at yr 3 was associated with baseline MetS (adjusted relative risk 4.09, 95% confidence interval 3.02–5.53, P < 0.001) and body mass index 30 kg/m² or greater (1.53, 1.17–1.99, P = 0.002) and increased risk (with a P value < 0.1) for GH dose 600 μg/d or greater (1.18, 95% confidence interval 0.98–1.44, P = 0.088).

Conclusion: MetS prevalence in GHD patients was higher than in the general population in the United States and higher in the United States than Europe. Prevalence was unaffected by GH replacement, but baseline MetS status and obesity were strong predictors of MetS after GH treatment.