GH deficiency (GHD) can be recognized in a not negligible proportion of thalassemic children, while data on the prevalence of this disorder in adult patients are lacking. Therefore, we elected to study the GH IGF-I axis in a large group of adult thalassemic subjects.
Study design: Ninety-four patients (69 with thalassemia major and 25 with thalassemia intermedia on stable transfusional regimen, 39 men and 55 women, aged 31.5±6.8 years, receiving sex steroid replacement when necessary) underwent a GHRH (1 μg/kg as an i.v. bolus)+arginine (0.5 g/kg as a 30 min i.v. infusion) test. Severe GHD was defined by GH peaks lower than 9 μg/l, whereas partial GHD was defined by GH peaks ranging from 9 to 16.5 μg/l. Blood samples for IGF-I, ferritin and pseudocholinesterase measurement were also performed.
Results: Severe GHD was demonstrated in 21/94 patients (22.3%), while 18 additional patients (19.1%) displayed partial GHD. No correlations were found between ferritin levels on one side and GH peaks and IGF-I SDS on the other side. GH peaks were positively correlated with IGF-I SDS (P<0.05), although 1 of the 21 patients with severe GHD showed normal IGF-I SDS values, and 45 of the 55 patients with normal GH reserve displayed low IGF-I SDS. A strong positive correlation (P<0.0001) between IGF-I SDS and pseudocholinesterase was shown.
Conclusions: a) This study has demonstrated a high prevalence of GHD, either partial or severe, in adult thalassemic patients. b) The lack of correlation between ferritin and both GH peaks and IGF-I SDS suggests that mechanisms other than iron overload play a major role in the pathophysiology of somatotropin-somatomedin deficiency in this clinical condition. c) The finding of a positive correlation between IGF-I SDS on one side and GH peaks and pseudocholinesterase values on the other side indicates that liver protidosynthetic activity, in addition to somatotropin secretory status, is a major determinant of IGF-I production in thalassemia.