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 suprasel lar 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 b etween the growth-promoting and metabolic effects of GH. We studied a 7.1 y ear old boy who, after removal of a suprasellar craniopharyngioma, develope d panhypopituitarism with mild hyperprolactinaemia. Despite the presence of severe GH deficiency associated with persistently low IGF-I and IGFBP-3 le vels, the patient grew spontaneously at an accelerated rate for a prepubert al boy, achieving a height velocity of 9.0 cm during the first and 8.5 cm d uring the second post-operative year. However, other metabolic parameters o f GH activity were adversely affected by the lack of GH. The maximum tubula r reabsorption rate for phosphate over glomerular filtration rate ratio (2. 8) was persistently low and normalized during a 4 day course of hGH adminis tration (4.2) together with the normalization of IGF-I (from 34 mug/l to 29 4 mug/l), suggesting that GH-dependent renal phosphate handling is impaired in this syndrome. In addition, bone age was delayed by 1.7 years consisten tly with delayed skeletal maturation, whereas skinfold thickness and the wa ist to hip ratio were increased in comparison with normative data, suggesti ng increased adipose tissue mass with central fat distribution, a phenotype characteristic of GH deficiency. In conclusion, our case study suggests th at, in the "growth without GH" syndrome, the excessive growth is independen t of GH and dissociated from other GH-dependent metabolic effects, which ar e decreased. (C) 2001 Harcourt Publishers Ltd.