Adult GH deficiency - the value of IGF-I estimation

In patients with growth hormone (GH) deficiency (GHD) the diagnostic value of IGF-I levels has been recently revisited. A normal IGF-I value does not exclude GHD, because its secretion is complex and depends by several factors other than GH, such as age, nutritional status, obesity, as well as catabolic illness. Due to the complexity and costs of GH stimulation tests, several authors have analyzed the predictive and diagnostic value of the concentration of plasma IGF-I in patients suspected for GHD. The evaluation of IGF-I is also determinant to individualized dose-titration strategies, able to avoid the common adult side effects of substitutive therapy with recombinant GH. Current recommendations in clinical practice for GH replacement therapy, in GHD adults, agree on GH dosing regimens to be individualized independently of body weight using IGF-I levels as a biomarker of the treatment. For these reasons, in a clinical setting, appropriate normative values in different age groups in a large healthy population must be established in single laboratories, while, considering the relatively small sex difference, a different reference range for sex seems not necessary. This review discusses the more recent debated issues in the literature on the role of IGF-I, as well as other IGF system components, in the management of adult patients with GHD