Safety in growth hormone replacement therapy: a matter of varied responsiveness?

Many studies of dosing and pharmacokinetics in growth hormone (GH) replacement therapy have been conducted, whereas there have been few studies examining GH sensitivity and individual responses to GH. It is probable that sensitivity to GH in terms of beneficial effects will be different from sensitivity in terms of fluid retention. Several factors, including age, body mass index and GH-binding protein levels have been implicated in growth and metabolic responses to GH in children and adults, respectively. Fluid retention during GH replacement in adults has been linked to age, body mass and body mass index. These conclusions are broadly supported by data from KIMS (Pharmacia International Metabolic Database), which also show that women are more susceptible than men to symptoms of fluid retention during GH replacement. Very few children undergoing GH therapy experience fluid retention, and thus it is difficult to draw conclusions about sensitivity. In the future, multiple regression analysis may be a useful tool for fully understanding the factors involved in individual responses to GH replacement.