Does bright light suppress nocturnal melatonin secretion more in women than men?

Abstract

Sex differences in the sensitivity of the human pineal gland to the suppressant effect of bright light on melatonin synthesis were studied in 6 healthy men and women. Blood samples were collected in two randomly ordered sessions: in one, subjects rested supine in bed, in the dark, from 21.00 to 7.00 h; in the other session, they were exposed to bright light (2,000 lux) from 2.00 to 4.00 h. In the dark condition, no significant differences were observed between men and women in either the timing or the absolute values of melatonin plasma levels, whereas after bright light exposure, the suppression of plasma melatonin was a 40% greater in women than in men. These findings suggest that, in humans, there is a sex difference in the nocturnal sensitivity of the pineal to light.

Light-induced melatonin suppression: age-related reduction in response to short wavelength light

“…Two studies (Boyce and Kennaway, 1987;Nathan et al, 2000) have shown no significant gender difference in melatonin suppression using a range of intensities (200-3000 lux) of white light. These findings were in contrast to a report which showed females had a greater sensitivity to 2000 lux of white light in comparison to males (Monteleone et al, 1995). In a preliminary study comparing the response of young men and young women to monochromatic 456 and 548 nm light, although the young females showed reduced melatonin suppression compared to the men, these gender differences were not statistically significant (Skene, Middleton, Thapan, unpublished data).…”

Effect of Sodium Valproate on Nocturnal Melatonin Sensitivity to Light in Healthy Volunteers

“…Further, the synthesis of melatonin can be suppressed by exposing participants to bright nocturnal light (Lewy et al, 1980), an effect which is independent of age (Nathan et al, 1999a), season (Nathan et al, 1999c), menstrual oestrus in females (Nathan et al, 1999d), and differences in melatonin amplitude (Nathan et al, 1999a). While some studies show a gender effect in suppression (Monteleone et al, 1995), recent research in this laboratory showed sensitivity was consistent between males and females across various light intensities (Nathan et al, 1997).…”

Short term exposure to 1439 MHz pulsed TDMA field does not alter melatonin synthesis in rats

“…There appears to be a gender difference in the nocturnal sensitivity of the pineal gland to light [Monteleone et al, 1995]. It is reported that women showed a 40% greater suppression of the nocturnal plasma melatonin level than men when exposed to bright light.…”