New approach to the diagnosis of growth hormone deficiency in adults

Abstract

Ghigo E, Aimaretti G, Gianotti L, Bellone J, Arvat E, Camanni F. New approach to the diagnosis of growth hormone deficiency in adults. Eur J Endocrinol 1996;134:352–6. ISSN 0804–4643 Pyridostigmine (PD), a muscarinic cholinergic agonist, and arginine (ARG) clearly increase the growth hormone (GH) response to growth hormone-releasing hormone (GHRH) in man. The current study was undertaken to investigate the value and safety of PD + GHRH and ARG + GHRH tests as well as the measurement of serum insulin-like growth factor I (IGF-I) in diagnosing GH deficiency in adults. Fifty-four patients considered GH deficient from extensive organic or idiopathic pituitary disease and 326 healthy adults were studied. The IGF-I concentrations were lower than the 3rd percentile of normal values in only 31 of the 54 (57.4%) patients with hypopituitarism. However, the IGF-I levels in hypopituitary patients and in normal subjects overlapped more frequently between 41 and 60 years (50%) and between 61 and 80 years (92.3%) as opposed to between 20 and 40 years (8.6%). In contrast to the IGF-I measurement, the ranges of peak GH responses to PD + GHRH and ARG + GHRH tests were clearly differentiated between the hypopituitary (0.2–6.8 and 0.1–9.5 μg/l, respectively) and normal subjects 17.7–114 and 16.1–119 μg/l, respectively). However, the PD + GHRH test was reliable only in subjects of 20–40 years of age. In conclusion, IGF-I measurement had no value in the diagnosis of GH deficiency in adults aged over 40 years, but is reliable enough when young adults of 20–40 years of age are considered. Both PD + GHRH and ARG + GHRH testing should be considered more reliable biochemical measurements of GH deficiency. In contrast to the PD + GHRH test, the ARG + GHRH test is reliable throughout the adult lifespan and appears to be the most appropriate for patient compliance and safety. F Camanni, Divisione di Endocrinologia, Ospedale Molinette, C.so Dogliotti 14, 10126 Torino, Italy