The diagnosis of IGF-1 deficiency due to GH-IGF abnormalities must use the most appropriate parameters for age and pubertal stage. We propose the diagnosis of growth hormone deficiency (GHD) based in an hierarchy of clinical and laboratory data. Clinical evaluation and general laboratory tests, e.g. thyroid tests, permit to exclude other causes of IGF deficiency that are not intrinsic to the GH-IGF axis. In these, the measurement of serum IGF-1 must be the first step in prepubertal, pubertal and elderly groups of patients whereas free ALS is better among young adults. IGF-1 analysis can revel 4 different situations: very low, low, normal and high levels. IGF-1 lower than 35µg/L or -2 SD of mean for chronological age (SDS-CA) allows diagnosis of IGF-1 deficiency. In this situation, only 1 test for GH secretion is necessary to differentiate GH deficiency and GH insensitivity. IGF-1 generation test can confirm GH insensitivity. IGF-1 lower than 70µg/L in prepubertal or adult patients and IGF-1 lower than 170µg/L in pubertal subjects, or between -2 and -1 SDS-CA, suggest IGF-1 deficiency. Two tests to assess GH secretion are recommended. Sub-normal GH peak in 2 tests confirm the diagnosis of GHD. These patients should undergo image test in order to search for hypothalamus-pituitary morphological abnormalities. Normal GH peak prompts to nocturnal GH physiological profile in order to run out the possibility of neurosecretory GH dysfunction when there are strong clinical evidences of IGF deficiency and low serum IGF-1 levels. IGF-1 higher than -1 SD but lower than the mean for chronological age suggests no IGF-1 deficiency. High IGF-1 level imposes the IGFBPs determination and consideration of IGF-1 resistance. Although the difficulties, all effort has to be made in order to diagnose properly the abnormalities of GH-IGF axis and install the adequate therapy.
Growth hormone deficiency; Growth hormone; IGF-1
