No abstract

The causes of growth retardation of children with thalassaemia major are multifactorial. We studied the GH response to provocation by clonidine and glucagon, measured the circulating concentrations of insulin, IGF-I, IGF-binding protein-3 (IGFBP-3) and ferritin, and evaluated IGF-I generation after a single dose of GH (0.1 mg/kg per dose) in 15 prepubertal patients with thalassaemia, 15 age-matched children with constitutional short stature (CSS) (height standard deviation score less than ¹2, with normal GH response to provocation) and 11 children with isolated GH deficiency (GHD). Children with thalassaemia had significantly lower peak GH response to provocation by clonidine and glucagon (6:2 Ϯ 2:3 and 6:8 Ϯ 2:1 mg/l respectively) than the CSS group (18:6 Ϯ 2:7 and 16:7 Ϯ 3:7 mg/l respectively). They had significantly decreased circulating concentrations of IGF-I and IGFBP-3 (47:5 Ϯ 19 ng/ml and 1:2 Ϯ 0:27 mg/l respectively) compared with those with CSS (153 Ϯ 42 ng/ ml and 2:06 Ϯ 0:37 mg/l respectively), but the IGF-I and IGFBP-3 concentrations were not different from those with GHD (56 Ϯ 25 ng/ml and 1:1 Ϯ 0:32 mg/l respectively). These data demonstrate that the GH-IGF-I-IGFBP-3 axis in thalassaemic children is defective. Serum ferritin concentration correlated significantly with GH peak response to provocation (r ¼ ¹0:36, P < 0:05) and circulating IGF-I (r ¼ ¹0:47, P < 0:01) and IGFBP-3 (r ¼ ¹0:42, P < 0:01) concentrations. In the IGF-I generation test, after GH injection, the thalassaemic children had significantly lower IGF-I and IGFBP-3 levels 86:7 Ϯ 11:2 ng/ml and 2:05 Ϯ 0:51 mg/l respectively) than those in the CSS group (226 Ϯ 45:4 ng/ ml and 2:8 Ϯ 0:43 mg/l respectively). The IGF-I response was significantly higher in children with GHD (158 Ϯ 50 ng/ml) than in thalassaemic children. Six short (height standard deviation score less than ¹2) thalassaemic children who had defective GH response to provocation (<10 mg/l), all the children with GHD and eight short normal children (CSS) were treated for 1 year with human GH (18 units/m 2 per week divided into daily s.c. doses). After 1 year of GH therapy there was a marked acceleration of growth velocity in both thalassaemic children (from 3:8 Ϯ 0:6 cm/year to 7:2 Ϯ 0:8 cm/year) and controls. However, the linear acceleration of growth velocity on GH therapy was significantly slower in thalassaemic children (3:3 Ϯ 0:3 cm/year increment) compared with those with CSS (5:3 Ϯ 0:4 cm/year increment) and GHD (6:9 Ϯ 1:2 cm/year increment) (P < 0:05). Their circulating IGF-I concentration (105 Ϯ 36 ng/ml) was significantly lower than those for CSS (246 Ϯ 58 ng/ml) and GHD (189 Ϯ 52 ng/ml) after 1 year of GH therapy. These data prove that some children with b-thalassaemia major have a defective GH-IGF-I-IGFBP-3 axis and suggest the presence of partial resistance to GH.

To determine the effect of ventricular function, size of ventricular septal defect (VSD), and endocrine function on linear growth in children with VSD, we studied 88 children with VSD over a period of 1 year. Growth was assessed by determining the height standard deviation scores (HtSDS) and growth velocity (GV) every 4 months. Two hundred age-matched normal children served as controls for the growth data. Endocrine evaluation was performed in 30 randomly selected children with VSD, and 20 age-matched children with constitutional delay of growth (CSS). Growth hormone (GH) response to clonidine provocation was evaluated and circulating free thyroxine (FT4) and insulin-like growth factor-I (IGF-I) concentrations measured. Echocardiographic evaluation of the different cardiac parameters including shunt size and shunt fraction (Qp/Qs) was performed using a colour-coded echodoppler. The HtSDS, body mass index (BMI), and mid-arm circumference (MAC) of children with VSD were significantly decreased compared to those for the normal control group. The dietary intake evaluated by the recall method, appeared to be adequate in the majority of these children (83/88). IGF-I concentrations were reduced in children with VSD (87.5 +/- 29 ng/ml) versus normal age-matched children (169 +/- 42 ng/ml). Basal and clonidine-stimulated GH concentrations were significantly higher in children with VSD (4.6 +/- 2.1 microg/l and 28.8 +/- 7.9 microg/l respectively) versus controls (17.8 +/- 4.2 microg/l). In these patients (n = 88) the HtSDS was correlated negatively with the size of the shunt (r = -0.793, p < 0.001), shunt fraction (Qp/Qs) (r = -0.76, p < 0.001), pulmonary mean gradient (r = -0.4, p = 0.006), and pulmonary maximum velocity (r = -0.32, p = 0.02). Growth velocity (GV) was correlated negatively with pulmonary maximum gradient (r = -0.3, p = 0.02), pulmonary maximum velocity (r = -0.37, p = 0.007), and pulmonary stroke volume (Qp) (r = -0.345, p = 0.01). The BMI and IGF-I concentrations were correlated significantly with the size of the shunt (r = -0.453, p < 0.01), Qp/Qs (r = -0.432, p < 0.01), HtSDS (r = 0.565, p < 0.01), and BMI (r = 0.435, p < 0.01). It appears that in patients with VSD, the size of the left-to-right shunt and the abnormal hemodynamics in the pulmonary circulation are important factors in the etiology of impaired growth. It is suggested that the hypermetabolic status of these patients compromise nutrition and this decreases IGF-I synthesis with subsequent slowing of linear growth and weight gain.