Abstract
The somatotropic axis is intricately involved in normal sleep, as evidenced by the fact that hypothalamic growth hormone-releasing hormone (GHRH) has sleep promoting effects and pituitary growth hormone (GH) release is strongly associated with slow-wave sleep (SWS). Abnormalities in the somatotropic axis, such as GH deficiency of hypothalamic or pituitary origin, result in an alteration of normal sleep patterns which may explain the fatigue reported in these individuals. Sleep disorders such as narcolepsy, in which individuals abnormally enter rapid eye movement (REM) sleep at sleep onset are also associated with an altered GHRH circadian rhythm and abnormal GH secretion. While few studies are available, this review explores what is known about sleep abnormalities in GH deficiency, the effect of treatment on sleep in patients with GH deficiency, and GH secretion in narcolepsy. Emerging evidence suggests a hypothalamic link between narcolepsy and GH secretion. We also describe the unique constellation of isolated idiopathic GH deficiency and severe excessive sleepiness in adopted Nicaraguan siblings, one of which has narcolepsy and the other idiopathic hypersomnia.