Endocrine Abstracts

GH plays a crucial role not only for growth, but also for the acquisition of bone mass and muscle strength. This process is completed after the achievement of adult height in the phase of transition from adolescence to adulthood. Therefore, continuation of GH replacement therapy in the transition age is essential in patients with a childhood-onset diagnosis of GHD. Higher likelihood of persistence is ovserved in patients with an early age at diagnosis, anatomical, organic, or genetic causes, and MPHD. Repeating a GH stimulation test is not necessary for patients with MPHD (≥ 3 PHD) and low-serum IGF-1 concentrations (<–2.0 SDS), in patients with documented genetic defects affecting pituitary function, and in patients with hypothalamic-pituitary structural brain defects. In these cases, rhGH therapy can be continued without interruption, although the dose should be reduced to the adult age dose. Indeed, patients with idiopathic IGHD and an IGF-1 ≥ 0 SDS are not likely to have persistent GHD, and hence transition therapy may not be necessary. There is still controversy about which limit for a normal GH response should be considered for the transition age group, and the lack of strong evidence leads to variable clinical practice. According to the last Consensus of 2019, the ITT remains the gold-standard test for establishing the diagnosis of young adult GHD using a peak GH cut-point of ≤ 5.0 µg/l, while according to others the optimal GH cut-off value after adult height achievement is 6 µg/l. While recent data have suggested that combined GHRH and arginine is unreliable and may fail to recognize patients with permanent GHD of different etiologies, it should be emphasized that the validated normative data of glucagon-stimulation test and macimorelin in transition age are still lacking.