Sleep and active renin levels--interaction with age, gender, growth hormone and cortisol.

Aims: In young normal male subjects, plasma renin activity (PRA) shows large oscillations with a distinct association to the cyclic occurrence of rapid eye movement (REM) and non-REM (NREM) periods. Until now the sleep-related course of active renin levels is unknown. Furthermore, there are no data on the effects of age and gender on nocturnal renin and the interaction between these variables, sleep, growth hormone (GH) and cortisol.

Ghrelin suppresses secretion of FSH in males.

Background: Ghrelin decreases the secretion of LH probably by suppressing the release of hypothalamic GnRH. So far however, there is no evidence that ghrelin affects also the secretion of FSH in humans, the other gonadotrophin regulated by GnRH.

Objective: Our objective was to study the effect of ghrelin on secretion of FSH in humans.

Ghrelin alone or co-administered with GHRH or CRH increases non-REM sleep and decreases REM sleep in young males.

Ghrelin activates the somatotropic and the hypothalamic-pituitary-adrenal axes, being crucially involved in sleep regulation. Simplified, growth hormone releasing hormone (GHRH) increases slow-wave sleep and REM sleep in males, whilst corticotropin-releasing hormone (CRH) increases wakefulness and decreases REM sleep. Ghrelin's role in sleep regulation and particularly its interactions with GHRH and CRH are not entirely clear.