Suppression of the hypothalamus-pituitary somatotrope axis in men with spinal cord injuries

Thirty-two men with spinal cord injury (SCI) were studied for evaluation of the hypothalamus-pituitary somatotrope axis, using growth hormone-(GH)-releasing hormone (GHRH) and insulin-induced hypoglycemia. Twenty-six age-matched normal male volunteers served as controls. Six SCI subjects (18.7%) had elevated basal follicle-stimulating hormone (FSH) levels, eight (25.0%) had hyperprolactinemia, and 11 (34.4%) had reduced serum insulin-like growth factor-1 (IGF-1) levels. Twenty SCI subjects (62.5%) had reduced and/or delayed GH responses to GHRH, and eight (25.8%) had reduced GH response to insulin-induced hypoglycemia. Seven of eight hyperprolactinemic SCI subjects showed reduced GH response to GHRH and/or insulin-induced hypoglycemia. These findings are consistent with the notion that SCI subjects have a reduced central dopaminergic tone.