Growth hormone deficiency in the transition adolescent: should treatment be continued in adult life?

Adults with growth hormone (GH) deficiency (GHD) have impaired health, which improves with GH replacement. GHD in adulthood leads to impairment in body composition and structure functions as well as to deranged lipoprotein and carbohydrate metabolism leading to increased cardiovascular morbidity. Therefore the transition adolescent in whom severe GHD is confirmed has to continue GH replacement with an appropriate age-related dosage. All short children who have been treated with rhGH for classical and non-classical GHD should be suspected as potentially GHD in adulthood though only in classical organic and idiopathic forms is severe GHD likely to be confirmed. GHD must be shown biochemically by single provocative testing. Insulin-induced hypoglycemia (ITT) and GHRH + arginine are the tests of choice provided that appropriate cutoff limits are assumed; these tests show good specificity and sensitivity. Testing with GHRH + GH secretagogues is another reliable alternative. Low IGF-I levels can be definitive evidence of persistent severe GHD in patients with genetic GHD or panhypopituitarism, but normal IGF-I levels do not rule out severe GHD. Individual titration of the rhGH dose is recommended and measurement of IGF-I levels is needed for monitoring the adequacy of replacement. The mean GH dose for replacement in the transition adolescent, however, is still higher than in adulthood; after puberty the rhGH dose should be progressively decreased in the following years (probably up to 25 years old) in order to obtain optimal peak bone mass.