Growth hormone and sleep in Down syndrome

The aim of this study was to evaluate correlations between neurophysiological sleep parameters, already known to be abnormal, and growth hormone (GH) release in Down syndrome (DS). Nine DS patients (5 males and 4 females) underwent 1 polygraphic night recording after 1 adaptation night; blood samples were contemporarily collected, every 20 min, by means of a continuous withdrawal pump and the level of GH assessed by an immunoradiometric assay. Sleep recordings were visually scored, hypnograms were obtained and plotted together with the profiles of the release of GH, in each patient. GH peaks were analyzed by means of the PULSAR program. The same study was carried out in 1 control subject. DS patients showed a clearly decreased peak amplitude of GH during sleep, even if a certain pulsatility was evident in all of them. However, synchrony with the slow-wave sleep was poor in DS patients because only 22.7% of peaks occurred in such a stage. This study demonstrates that, if evaluated during sleep, GH release in DS subjects often shows a decrease in amplitude of peaks and altered time connection with the sleep structure. A useful application of the study of sleep is suggested in order to monitor changes in cognitive capabilities induced by the eventual introduction of GH therapy in DS patients.