Growth hormone releasing factor and assessment of growth hormone reserve in children

Abstract

Pituitary somatotrophic reserve was assessed in children with growth delay using clofelin and growth hormone releasing factor (GH-RH). Thirty-four children hospitalized with suspected insufficiency of growth hormone (GH) were examined (22 boys and 12 girls aged 5.3 to 16.2, mean age 11.6±3.2). Bone age lagged behind the chronologic by 4.4+2.1 years, and signs of puberty were absent by the moment of hospitalization in all the children. Clofelin was administered orally in a dose of 0.15 microg/m2 body surface, GH-RH by intravenous jet in a dose of 1 mg/kg. The patients were divided into 3 groups with different response of GH to stimulation with clofelin and GH-RH: group A with a low GH output in both test (the pituitary form); group В with a low reaction to clofelin and normal response to GH-RH (the hypothalamic form); group C with increased level of response to both clofelin and GH-RH (idiopathic dwarfism). Group A included 14 children aged 11.7±2.9. Growth SDS in these children varied from -7.8 to -2.6 (-4.4±1.66). The maximal GH level after clofelin intake was 1.3 ± 1.6 ng/ml and after GH-RH infusion 3.5±2.51 ng/ml in group A. Group В consisted of 7 patients aged 12.0±4.4. Growth SDS in this group varied from -5.6 to 2.5 (- 4.0±1.3). The maximal level of GH in this group was 2.5±2.4 ng/ ml in clofelin test and 15.9±5.4 ng/ml in GH-RH test. Group C included 13 children aged 11.0±4.4, with growth SDS varying from -4.3 to -2.3 (-3.0±0.63). The maximal GH level after clofelin was 15.6±8.2 and after GH-RH 40.8±26.1 ng/ml, this being reliably higher than in group В (U=16.5, p=0.02). Hence, somatotrophic insufficiency was caused by hypothalamic disorders in approximately one-third of our patients.