Small for gestational age (SGA): endocrine and metabolic consequences and effects of growth hormone treatment

Several studies have demonstrated an association between low birth weight and impaired insulin sensitivity or even type 2 diabetes mellitus (DM2) in later life. Growth hormone (GH) is known to increase fasting and postprandial insulin levels. For that reason concern has been expressed regarding possible detrimental effects of GH therapy in children born SGA. In a Dutch trial the possible side effects of GH therapy on carbohydrate metabolism were assessed in short children born SGA after 6 years and at 6 months after discontinuation of GH therapy. This study included 79 prepubertal short children born SGA, participating in a multicenter double-blind, randomized, dose-response GH trial. Inclusion criteria were: 1) birth length SDS below -1.88, 2) age 3-11 years in boys and 3-9 years in girls, 3) height SDS < -1.88, 4) no spontaneous catch-up growth, and 5) an uncomplicated neonatal period. Mean (SD) value for age was 7.3 (2.1) years, birth length SDS -3.6, height SDS -3.0 (0.7) and BMI SDS -1.2 (1.3). All children were randomly assigned to either group A (n = 41) using 1 mg GH/m2/day or group B (n = 38) using 2 mg/m2/ d/ay (approximately 0.1 or 0.2 IU/kg/d, respectively). Standard oral glucose tolerance tests (OGTTs) were performed before and during 6 years of GH therapy and 6 months after discontinuation of GH therapy. Before GH therapy 8% of the children had impaired glucose tolerance (IGT) according to criteria of the WHO. After 6 years of GH therapy, IGT was found in 4% and after stopping GH in 10%. Mean fasting glucose increased significantly with 0.5 mMol/l after 1 year of GH therapy, without a further increase thereafter. GH therapy induced considerably higher fasting and glucose-stimulated insulin levels. None of the observed changes were different between the GH dosage groups. Children who remained prepubertal had similar glucose and insulin levels compared to children who entered puberty. HbA1c levels were always in the normal range and none of the children developed diabetes mellitus. After discontinuation of GH therapy the mean serum glucose levels remained normal and the mean serum insulin levels decreased significantly, to normal age reference values. Before the start of GH the mean systolic blood pressure was significantly higher compared to age-matched peers, whereas during GH therapy a significant decline in mean systolic blood pressure occurred, which remained similar after discontinuation of GH treatment. In conclusion, continuous, long-term GH therapy in short children born SGA has no adverse effects on glucose levels, even with GH dosages up to 2 mg/m2/day. However, as has been reported in other patient groups, GH induced higher fasting and glucose-stimulated insulin levels, indicating insulin resistance. After discontinuation of GH, serum insulin levels declined to normal age-matched reference levels. Since impaired insulin sensitivity and DM2 have been demonstrated in relatively young patients born SGA, long-term follow-up of children born SGA is advised, also after discontinuation of GH therapy.