Genetic control of 24-hour growth hormone secretion in man: A twin study

The aim of this study was to delineate the contributions of genetic and env ironmental factors in the regulation of the 24-h GH secretion. The 24-h pro file of plasma GH was obtained at 15-min intervals in 10 pairs of monozygot ic and 9 pairs of dizygotic normal male twins, aged 16-34 yr. Sleep was pol ygraphically monitored. Significant pulses of GH secretion were identified using a modification of the computer algorithm ULTRA. For each significant pulse, the amount of GH secreted was calculated by deconvolution. A procedu re specially developed for twin studies was used to partition the variance of investigated parameters into genetic and environmental contributions. A major genetic effect was evidenced on GH secretion during wakefulness (with a heritability estimate of 0.74) and, to a lesser extent, on the 24-h GK s ecretion. Significant genetic influences were also identified for slow wave sleep and height. These data demonstrate that human GH secretion in young adulthood is markedly dependent on genetic factors.