GROWTH HORMONE SECRETION ON COMPLETION OF TREATMENT IN ISOLATED "IDIOPATHIC" AND POST-IRRADIATION GROWTH HORMONE DEFICIENCY

Abstract

After completion of growth hormone (GH) treatment, 19 patients with isolated “idiopathic” growth hormone deficiency (IGHD) and 15 with post-irradiation growth hormone deficiency (PRGHD) were asked to undergo retesting of GH secretion with an insulin tolerance test and/or an arginine stimulation test. PRGHD patients are those with CNS tumours distant from the hypothalamic-pituitary axis (n=13) or acute lymphatic leukaemia (n=2), who had received cranial or cranospinal irradiation.All 15 patients with PRGHD remained GH deficient [peak GH level <7mU/l (n=10) and 7-15mU/l (n=5)]. However of the 19 retested IGHD patients, 5 (26%) had peak GH responses >15mU/l (regarded now as transient or false F-IGD) and were indistinguishable from the remainder [permanent or true T-IGHD, peak GH levels <7mU/l (n=12) and 7-15 mU/1 (n=2)] by pre-treatment anthropometry and post-treatment height SDS, but had a lower first year height velocity (Mean Velocity 5.4cm/yr ±0.9 for F-IGHD v 8.7cm/year ±1.75 for T-IGHD p<0.01) and height acceleration on treatment (Mean acceleration 2.1cm/yr ±1.7 for F-IGHD v 5.2cm/yr ±2.3 for T-IGHD p<0.05). By current practices 2 F-IGHD patients may have been distinguished by sex-steroid priming.Thus post-irradiation GH deficiency appears to be permanent but errors of diagnosis in IGHD are common.