Mogul HR et al. (2008) Growth hormone treatment of adults with Prader Willi syndrome and growth hormone deficiency improves lean body mass, fractional body fat, and serum triiodothyronine without glucose impairment: results from the US multi-center trial. J Clin Endocrinol Metab [doi:10.1210/jc.2007-2212]

Children with Prader–Willi syndrome (PWS) receive growth-hormone (GH) replacement therapy. Small studies suggested that GH administration might also benefit adults with PWS; however, GH has multiple effects on glucose homeostasis, and might worsen patients' risks of developing diabetes or the metabolic syndrome.

Mogul and colleagues' 1-year, multicenter, US study evaluated open-label GH therapy in a phenotypically diverse cohort of 38 adults (age range 17–49 years, BMI range 22.0–63.6 kg/m2, 25 women) with genotype-confirmed PWS. All patients were GH-deficient and had not used GH therapy in the preceding 12 months. GH therapy was started at 0.2 mg daily and increased by 0.2 mg increments each month, as tolerated, unless IGF-I levels became elevated by ≥1 SD, in which case the GH dose was reduced to the previous level for the rest of the study. Following the dose-optimization phase, all patients' daily GH doses were kept constant for the rest of the study (mean dose 0.6 mg). GH therapy significantly increased lean body mass and decreased body fat, particularly in men, although BMI remained unchanged. All measures of insulin and glucose homeostasis remained within normal ranges, even in the five diabetic patients.

Patients with PWS are thought to have a normal thyroid axis, but 20% of this cohort had baseline T3 abnormalities that normalized with GH therapy. The authors suggest that peripheral T4–T3 conversion contributes to GH-mediated enhancement of resting energy expenditure, which increases lean body mass. GH therapy also improved patients' energy levels, attention span, and wellbeing.