The 24-h pattern of human prolactin and growth hormone in healthy elderly subjects.

Determination of plasma prolactin concentration every 2 h in twelve healthy elderly subjects, aged between 62 and 78, indicates that the secretory rhythm is not modified with age and that it remains synchronized with the sleep-wake cycle. The increase of awake time during the night in old age does not change substantially the rise of nocturnal prolactin levels. The 24-h profile of growth hormone is characterized by a frequent decrease or absence of sleep-related peaks in elderly subjects. This reduction of growth hormone nocturnal secretion does not seem secondary to an alteration in sleep structure.