USE OF INSULIN-LIKE GROWTH-FACTOR-I (IGF-I) AND IGF-BINDING PROTEIN-3IN THE DIAGNOSIS OF ACROMEGALY AND GROWTH-HORMONE DEFICIENCY IN ADULTS

The goal of our study was to compare the clinical usefulness of plasma insulin-like growth factor-I (IGF-I) (with and without binding protei n extraction) and IGF binding protein-3 (IGFBP-3) measurements in the diagnosis of growth hormone (GH) disorders hu adults. IGF-I and IGFBP- 3 concentrations were measured in 25 acromegalic and 25 GH-deficient a dult (GHDA) subjects (20-76 years) by comparison to a control populati on (n = 81) after age and ses stratification. In untreated acromegaly, IGF-I and IGFBP-3 were clearly increased (10 times the mean of contro ls for unextracted IGF-I, 4 times for extracted IGF-I and 2 times for IGFBP-3). Using the mean + 2SD of the control population as the cut-of f point, the sensitivity of IGF-I for the diagnosis of acromegaly was higher than that of IGFBP-3 (unextracted IGF-I: 96% and extracted IGF- I: 100% vs IGFBP-3: 76%). In GHDAs, IGF-I and IGFBP-3 were decreased ( 34% of the mean of controls for unextracted IGF-I, 37% for extracted I GF-I and 70% for IGFBP-3). Using the mean - 2SD of the control populat ion as the cut-off point, the sensitivity of IGF-I measurement for the diagnosis of GHDA was relatively low, but better for unextracted (68% ) than for extracted IGF-I (52%). The sensitivity of IGFBP-3 was much lower (36%), thus invalidating this parameter for the diagnosis of GHD A. Our observations demonstrate that IGF-I measurement is a more power ful tool than IGFBP-3 measurement for the diagnosis of GH disorders in adults. Both IGF-I and IGFBP-3 are very useful for the diagnosis of a cromegaly, but they are less reliable for diagnosing GHDA, as normal I GF-I or IGFBP-3 values do not rule out GH deficiency.