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In November 2000 the Department of Health in England granted a licence to Pharmacia Limited for the use of their recombinant growth hormone, Genotropin (somatropin rbe), in the Prader-Willi syndrome. The indications for use were given as “improvement of body composition and growth”. In this leading article we shall attempt to examine the role of growth hormone in the Prader-Willi syndrome by considering linear growth and body composition in untreated and treated individuals, the pathophysiology of the abnormal linear growth, and the scope for future research.
While the growth and body composition aspects of the Prader-Willi syndrome are important, they must be seen in the context of a disabling disorder with major implications for the individual and family.1 Therefore a brief account of the condition is in order.
GENERAL ASPECTS OF THE PRADER-WILLI SYNDROME
The Prader-Willi syndrome results from loss of an imprinted gene or genes on the long arm of chromosome 15 within the q11–13 region, usually as a result of a deletion on the paternal chromosome or less commonly to inheritance of both chromosomes from the mother—maternal disomy.2 The gene(s) presumably encode(s) a protein or proteins important for brain development, loss of which leads to a generalised brain disorder which affects the hypothalamus in particular.3 Indeed, many of the characteristic traits of the syndrome, such as hyperphagia, somnolence, skin picking, and hypogonadism, are attributable to hypothalamic dysfunction.
Severe hypotonia and weakness cause reduced fetal movements, poor feeding from birth, usually requiring tube feeding, weak or absent cry, and inertia during infancy, with developmental delay and failure to thrive. Tone and movement improve towards the end of the first year and developmental milestones are achieved, albeit delayed. By 2 or 3 years of age the hyperphagic phase of the condition begins, and unless diet is strictly …