Background: In children with Prader-Willi syndrome (PWS), the benefits of growth hormone treatment are well established. Several one-year studies have shown that growth hormone is also beneficial for adults with PWS, improving body composition. However, little is known about the longer-term effects. This study investigated the effects on body composition in adult patients with PWS during 3 years of growth hormone therapy in a dose of 0.33 mg/m2/day. Methods: Open-label, prospective study in 43 young adults with PWS with a median (IQR) age of 19.0 (17.5 to 20.7) years. Fat mass percentage SDS and lean body mass SDS were measured annually by DXA. Results: Estimated mean (95% CI) fat mass percentage SDS decreased during the three-year study from 2.1 (1.9 to 2.3) SDS at start to 1.9 (1.8 to 2.1) SDS, p = 0.012, while lean body mass SDS remained stable at - 2.1 (- 2.4 to - 1.8) SDS at start to - 1.9 (- 2.3 to - 1.6) after 3 years, p = 0.15. Fasting glucose and insulin remained similar during the three-year study, glucose being 4.6 (4.4 to 4.8) mmol/l at start and 4.6 (4.5 to 4.7) mmol/l after 3 years of growth hormone, p = 0.93 and insulin being 59.5 (42.2 to 81.5) pmol/l and 55.0 (42.4 to 69.2) pmol/l, resp., p = 0.54. There were no growth hormone-related adverse events during the study. Conclusions: Three years of growth hormone treatment in young adults with PWS maintains the positive effects on body composition attained during childhood. Thus, adults with PWS benefit from longer-term growth hormone treatment. Trial registration: EudraCT, EudraCT number 2011-001313-14. Registered 17 October 2012.

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Keywords Adults, Body composition, Growth hormone, Prader Willi syndrome
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Journal Orphanet journal of rare diseases
Organisation Department of Pediatrics
Damen, L, Donze, S.H, Kuppens, R.J, Bakker, N.E. (Nienke E.), Bakker, N.E, de Graaff, L.C.G, … Hokken-Koelega, A.C.S. (2020). Three years of growth hormone treatment in young adults with Prader-Willi syndrome: Sustained positive effects on body composition. Orphanet journal of rare diseases, 15(1). doi:10.1186/s13023-020-01440-6