Optimizing GH therapy in adults and children

Until the advent of modern neuroradiological. imaging techniques in 1989, a diagnosis of GH deficiency in adults carried little significance other tha n as a marker of hypothalamopituitary disease. The relatively recent recogn ition of a characteristic clinical syndrome associated with failure of spon taneous GH secretion and the potential reversal of many of its features wit h recombinant human GH has prompted a closer examination of the physiologic al role of GH after linear growth is complete. The safe clinical practice o f GH replacement demands a method of judging overall GH status, but there i s no biological marker in adults that is the equivalent of linear growth in a child by which to judge the efficacy of GH replacement. Assessment of op timal GH replacement is made difficult by the apparent diverse actions of G H in health, concern about the avoidance of iatrogenic acromegaly, and the growing realization that an individual's risk of developing certain cancers may, at least in part, be influenced by cumulative exposure to the chief m ediator of GH action, IGF-I. As in all areas of clinical practice, strategi es and protocols vary between centers, but most physicians experienced in t he management of pituitary disease agree that GH is most appropriately begu n at low doses, building up slowly to the final maintenance dose. This, in turn, is best determined by a combination of clinical response and measurem ent of serum IGF-I, avoiding supraphysiological. levels of this GH-dependen t peptide. Numerous studies have helped define the optimum management of GH replacement during childhood. The recent requirement to measure and monito r GH status in adult life has called into question the appropriateness of s implistic weight- and surface area-based dosing regimens for the management of GH deficiency in childhood, with reliance on linear growth as the sole marker of GH action. It is clear that the monitoring of parameters other th an linear growth to help refine GH therapy should now be incorporated into childhood GH treatment protocols. Further research will be required to defi ne the optimal management of the transition from pediatric to adult GH repl acement; this transition will only be possible once the benefits,of GH in m ature adults are defined and accepted by pediatric and adult endocrinologis ts alike.