A study of the growth-promoting and metabolic effects of growth hormone (GH) in a patient with the "growth without GH" syndrome.

The paradox of normal or even excessive growth despite a proven lack of GH is a well-known but still unexplained phenomenon that has been described in some patients following resection of a craniopharyngioma or other suprasellar tumours. However, the consequences of GH deficiency on other metabolic aspects of GH action in this syndrome have not been adequately investigated. The aim of this study was to examine whether a dissociation might exist between the growth-promoting and metabolic effects of GH. We studied a 7.1 year old boy who, after removal of a suprasellar craniopharyngioma, developed panhypopituitarism with mild hyperprolactinaemia. Despite the presence of severe GH deficiency associated with persistently low IGF-I and IGFBP-3 levels, the patient grew spontaneously at an accelerated rate for a prepubertal boy, achieving a height velocity of 9.0 cm during the first and 8.5 cm during the second post-operative year. However, other metabolic parameters of GH activity were adversely affected by the lack of GH. The maximum tubular reabsorption rate for phosphate over glomerular filtration rate ratio (2.8) was persistently low and normalized during a 4 day course of hGH administration (4.2) together with the normalization of IGF-I (from 34 microg/l to 294 microg/l), suggesting that GH-dependent renal phosphate handling is impaired in this syndrome. In addition, bone age was delayed by 1.7 years consistently with delayed skeletal maturation, whereas skinfold thickness and the waist to hip ratio were increased in comparison with normative data, suggesting increased adipose tissue mass with central fat distribution, a phenotype characteristic of GH deficiency. In conclusion, our case study suggests that, in the "growth without GH" syndrome, the excessive growth is independent of GH and dissociated from other GH-dependent metabolic effects, which are decreased. Copyright 2001 Harcourt Publishers Ltd.