Determination of insulin-like growth factor-I in the monitoring of growth hormone treatment with respect to efficacy of treatment and side effects: Should potential risks of cardiovascular disease and cancer be considered

Insulin-like growth factor (IGF)-I has proven to be important in the diagno sis of childhood-onset growth hormone (GH) deficiency (GHD). However, the v ariability of IGF-I should be taken into account before it can be used in a clinical setting. GH replacement therapy in GHD patients increases IGF-I i nto the normal range, although there is a large variation. Excessively high (supranormal) GH-induced IGF-I levels are associated with increased preval ence of side effects in adults with GHD. Consequently, at most centres, GH doses are titrated according to IGF-I levels in GHD adults. Whether or not this should also be done in children has not been established. Due to the k nown variability of IGF-I, individual changes in IGF-I must exceed approxim ately 35% to be sufficiently significant to warrant a dose adjustment. Nove l epidemiological studies have suggested that higher IGF-I levels are assoc iated with an increased risk of prostate, breast and colorectal cancer comp ared with lower IGF-I levels in otherwise healthy subjects. Consequently, l ife-time exposure to IGF-I should be considered in all patients treated wit h GH, and IGF-I should preferably be kept with in normal age-related ranges in children as well as in adults. Copyright (C) 1999 S. Karger AG, Basel.