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

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.