Plasma IGF-I is a useful marker of growth hormone deficiency in adults

Diagnosing growth hormone deficiency in adults is difficult. Provocation te sts are most commonly used for the diagnosis with the insulin-induced hypog lycemia test nowadays considered as the "gold standard". The role of IGF-I concentrations in diagnosing growth hormone deficiency in adults is under d iscussion. In 58 adult patients with proven growth hormone deficiency, the sensitivity and specificity of IGF-I concentrations in relation to growth h ormone deficiency were evaluated. Reference values of plasma IGF-I were obt ained from 53 healthy volunteers. Using a calculated cut-off concentration of 15 nmol/l we were able to demonstrate that IGF-I concentration is a reli able screening method for growth hormone deficiency. Using this cut-off poi nt in a patient population younger than 40 years of age, sensitivity was 90 % and specificity 89%, For patients exceeding the age of 40 years, sensitiv ity, specificity and positive predictive value were rather low, but the neg ative predictive value was as high as 90%, indicating that for patients ove r 40 years IGF-I concentrations above 15 nmol/l exclude growth hormone defi ciency. In summary, under the age of 40 years measuring plasma IGF-I provid es an useful tool to diagnose growth hormone deficiency, whereas above 40 p lasma IGF-I values exceeding 15 nmol/l virtually exclude growth hormone def iciency. (C) 1999, Editrice Kurtis.