Absence of an increase in the duration of the circadian melatonin secretory episode in totally blind human subjects

• Published in: The journal of clinical endocrinology and metabolism Vol. 86; no. 7; pp. 3166 - 3170
• Main Authors: Klerman, E. B., Zeitzer, J. M., Duffy, J. F., Khalsa, S. B., Czeisler, C. A.
• Format: Journal Article
• Language: English
• Published: Legacy CDMS Endocrine Society 01.07.2001
• Subjects: Adolescent; Adult; Aged; Aged, 80 and over; Biological and medical sciences; Blindness - physiopathology; Circadian Rhythm; Female; Fundamental and applied biological sciences. Psychology; Hormones and neuropeptides. Regulation; Humans; Hypothalamus. Hypophysis. Epiphysis. Urophysis; Life Sciences (General); Male; Medical sciences; Melatonin - metabolism; Middle Aged; Ophthalmology; Time Factors; Vertebrates: endocrinology; Vision disorders; Human; Support, U.s. Gov't, Non-P.h.s; Blindness/physiopathology; Middle Aged; Support, U.s. Gov't, P.h.s; Non-Nasa Center; Male; Circadian Rhythm; Aged, 80 And Over; Time Factors; Nasa Discipline Regulatory Physiology; Adolescent; Female; Adult; Aged; Melatonin/secretion; Melatonin; Pathophysiology; Vision disorder; Circadian rhythm; Blood plasma; Endocrine secretion; Eye disease; Blindness; Hormonal regulation; Hormonal investigation; Elderly; Pineal hormone; NASA Discipline Regulatory Physiology; Non-NASA Center
• ISSN: 0021-972X
• DOI: 10.1210/jc.86.7.3166

The daily rhythm of melatonin influences multiple physiological measures, including sleep tendency, circadian rhythms, and reproductive function in seasonally breeding mammals. The biological signal for photoperiodic changes in seasonally breeding mammals is a change in the duration of melatonin secretion, which in a natural environment reflects the different durations of daylight across the year, with longer nights leading to a longer duration of melatonin secretion. These seasonal changes in the duration of melatonin secretion do not simply reflect the known acute suppression of melatonin secretion by ocular light exposure, but also represent long-term changes in the endogenous nocturnal melatonin episode that persist in constant conditions. As the eyes of totally blind individuals do not transmit ocular light information, we hypothesized that the duration of the melatonin secretory episode in blind subjects would be longer than those in sighted individuals, who are exposed to light for all their waking hours in an urban environment. We assessed the melatonin secretory profile during constant posture, dim light conditions in 17 blind and 157 sighted adults, all of whom were healthy and using no prescription or nonprescription medications. The duration of melatonin secretion was not significantly different between blind and sighted individuals. Healthy blind individuals after years without ocular light exposure do not have a longer duration of melatonin secretion than healthy sighted individuals.