Safety of growth hormone treatment in children born small for gestational age: the US trial and KIGS analysis.

BACKGROUND

Recently, growth hormone (GH) therapy for children with short stature born small for gestational age (SGA) has been approved in the USA and Europe. There have been few reports examining adverse events during GH treatment of these children.

AIMS

(i) To examine glucose tolerance and insulin sensitivity during GH treatment of children born SGA in a US trial. (ii) To determine and compare adverse events reported in children born SGA with those reported in children with idiopathic short stature (ISS) enrolled in KIGS - Pfizer International Growth Database.

METHODS

In the US SGA trial, an oral glucose tolerance test was performed and fasting plasma glucose, insulin and glycosylated haemoglobin (HbA(1C)) concentrations were measured at baseline and after 12 months of GH therapy. Insulin sensitivity was calculated using the homeostasis model assessment (HOMA) and the quantitative insulin sensitivity check index (QUICKI). In the KIGS analysis, a retrospective audit of spontaneously logged cumulative adverse events in children born SGA and those with ISS was undertaken. Adverse events are reported per 1,000 patients. Values are expressed as mean with 10th-90th percentiles.

RESULTS

In the US trial, 84 patients had complete data sets for analysis. Median birth weight was 1.78 kg (SDS, -2.5) and birth length 43 cm (SDS, -2.2) at a median gestational age of 36.5 weeks; 79% were Caucasian. At entry, median age of the patients analysed was 6.6 years, and 65% were male. Median height was 104.3 cm (SDS, -2.97), median weight 15.95 kg (SDS, -2.21) and body mass index 14.66 kg/m(2) (SDS, -0.67). No patients developed impaired glucose tolerance or overt diabetes mellitus. The 0-min glucose concentration was 81 mg/dl at baseline and 86 mg/dl at 1 year, while the 120-min glucose concentration was 90 mg/dl at baseline and 96 mg/dl at 1 year. The 0-min insulin concentrations were 2.9 mU/l at baseline and 5.3 mU/l at 1 year, while the 120-min insulin levels were 7.7 mU/l at baseline and 11 mU/l at 1 year. The proportions of HbA(1C) were 5.2 and 5.4% at baseline and 1 year, respectively. HOMA and QUICKI values were 0.59 and 0.42, respectively, at baseline, and 1.13 and 0.38 at 1 year. In KIGS, there were 1909 children born SGA aged 9.1 (3.9-13.3) years with a birth weight SDS of -2.6 (-4.0 to -1.5), birth length SDS of -2.7 (-4.3 to -1.3) and height SDS of -2.71 (-3.9 to -1.8) prior to treatment. GH doses ranged from 0.032 to 0.037 in the USA and from 0.022 to 0.023 mg/kg/day in the remaining countries in KIGS. Neither total (187 vs. 183) nor serious (14 vs. 10) adverse events occurred more commonly in the SGA group than in the ISS group. Although respiratory adverse events occurred more commonly in children born SGA (34.3 vs. 16.8; p < 0.05), endocrine (12.0 vs. 2.7; p < 0.05) and hepatobiliary (6.2 vs. 1.1; p < 0.05) adverse events occurred more commonly in children with ISS.

CONCLUSIONS

As expected, a reduction in insulin sensitivity occurred during GH treatment of children born SGA; however, glucose tolerance remained normal. No adverse events were reported more commonly in children born SGA than in those with ISS. Minor differences in adverse events reporting within organ systems between children born SGA and those with ISS are probably due to variable under-reporting of adverse events. GH appears to be a safe drug to use at current doses as a growth-promoting agent in short children born SGA.