Sex difference in growth hormone response to growth hormone-releasing hormone between pubertal tall girls and boys.

In adult rats and also in young adults, a sex difference in GH responsiveness to GHRH has been reported with the higher responses in males. In young rats, however, the reverse has been found, i.e. a higher GH response in females than in males. This discrepancy promoted us to compare GH responsiveness to GHRH in midpubertal tall girls (N = 10) and boys (N = 8). An iv bolus administration of 100 micrograms of GHRH to these adolescents disclosed a sex difference in GH responsiveness. At all time intervals up to 30 min after the bolus, the GH responses to GHRH in the girls were significantly higher than in the boys (P less than 0.025 - P less than 0.05), whereas the peak GH increments (34 +/- 4 vs 19 +/- 3 micrograms/l; P less than 0.02) were about twice as high in the former as in the latter. The data suggest that like in rats, also in humans, sex-related changes in pituitary GH sensitivity to GHRH may be an important factor in the pubertal growth and development at least in tall girls and boys.