Cervical spinal cord lesions disrupt the rhythm in human melatonin excretion.

To determine whether spinal cord lesions disrupt the diurnal activity of the human pineal, urinary melatonin levels were measured over 24 hours (4 or 8-hourly intervals) in male patients with clinical evidence of cervical spinal cord transection. During the waking state, levels of melatonin in these subjects ranged from 3.2--13.5 ng/4 hours; during sleep and darkness, values ranged from 1.8--10.5 ng/4 hours. Levels of serum cortisol, aldosterone, and growth hormone showed rhythmic variations in these subjects. The absence of significant nocturnal melatonin increases distinguishes quadriplegic subjects from normal males and from one subject with a lesion of the lumbar spinal cord. These differences may be caused by "decentralization" of the pineal organ due to a lesion within the cervical spinal cord interrupting descending sympathetic fibers. If so, the human pineal, like that of other mammals, is regulated, at least in part, by activity within the central nervous system via sympathetic nervous connections.