Sleep and Rhythmic Profile After Pineal Gland Removal in Humans

Melatonin, a hormone produced by the pineal gland, is classically described as a central circadian modulator. However, the impact of its absence on circadian rhythmicity in humans remains poorly understood. Pinealectomised patients, in whom melatonin secretion is chronically suppressed, represent a valuable clinical model to investigate the physiological role of this hormone in sleep and temporal organisation. This study evaluated sleep quality and sleep disorders, as well as circadian rhythmicity, in 17 individuals who underwent surgical or radiotherapeutic treatment for pineal tumours and exhibited confirmed absence of circulating melatonin. Participants were assessed through structured clinical interviews, standardised sleep questionnaires, sleep diaries and actigraphy recording for a minimum of 15 consecutive days. Rhythmic analysis was performed for sleep/wakefulness and rest/activity data. Mild nocturnal sleep symptoms were reported, but diurnal complaints were frequent. Despite the chronic absence of melatonin, all subjects maintained a 24-h sleep/wake cycle, and none met criteria for circadian sleep/wake disorders. We conclude that melatonin demonstrated not to be crucial for the maintenance of the circadian sleep/wake cycle in individuals with chronic melatonin absence due to pineal gland removal and minor sleep complaints are present in this population. Other synchroniser mechanisms possibly involving non-photic entrainment might play an important role in the maintenance of the circadian rhythm.