Twenty-four-hour secretory patterns of growth hormone, prolactin, and cortisol in narcolepsy

Twenth-four-hour patterns of plasma GH, PRL, and cortisol concentrations concomitant with sleep stages were studied in four male patients with typical narcolepsy, aged 30--34 yr, and four normal subjects. All medications were withdrawn 2 weeks before the study. Blood was drawn every 20 min during a 24-h fasting period, except for the first sleep cycle of nocturnal sleep when samples were drawn at 5-min intevals. In all of the narcoleptics, a plasma GH peak associated with slow wave sleep at the nocturnal sleep onset was absent (n = 2) or markedly decreased (n = 2). The normal rise of PRL during sleep was present only in a narcoleptic, whereas a significant fall in plasma PRL concentrations occurred immediately after the sleep-onset rapid eye movement period and lasted 1--1.5 h in the remaining three patients. A sleep-onset rapid eye movement period occurred in all of the patients, and this abnormal phenomenon characteristic of narcolepsy was considered to be related to the suppression of GH release at the sleep onset and to the decrease of plasma PRL levels during the early part of sleep. In contrast, the normal circadian periodicity of cortisol secretion was evident in all of the narcoleptics.