Stimulatory Effect of Morning Bright Light on Reproductive Hormones and Ovulation: Results of a Controlled Crossover Trial

Abstract

Objectives:Studies have shown a shortening of the menstrual cycle following light exposure in women with abnormally long menstrual cycles or with winter depression, suggesting that artificial light can influence reproductive hormones and ovulation. The study was designed to investigate this possibility.Design:Placebo-controlled, crossover, counterbalanced order.Setting:Medical centres and participants' homes in Novosibirsk (55°N), Russia.Participants:Twenty-two women, aged 19–37 years, with baseline menstrual cycle length 28.1–37.8 d and no clinically evident endocrine abnormalities completed the study. The study lasted for two menstrual cycles separated by at least one off-protocol cycle.Interventions:During one experimental cycle, bright light was administered at home for 1 wk with a light box emitting white light at 4,300 lux at 41 cm for 45 min shortly after awakening. During the other experimental cycle, dim light was <100 lux at 41 cm with a one-tube fluorescent source.Outcome Measures:Blood samples and ultrasound scans were obtained in the afternoon before and after the week of light exposure, on day ∼7 and 14 after menstruation onset. Further ultrasound scans after day 14 documented ovulation. Serum was assayed for thyroid-stimulating hormone (TSH), prolactin (PRL), luteinizing hormone (LH), follicle-stimulating hormone (FSH), and estradiol (E2).Results:Concentrations of PRL, LH, and FSH were significantly increased with bright versus dim light exposure, as was follicle size (ANOVA, intervention × day, p = 0.0043, 0.014, 0.049, and 0.042, respectively). The number of ovulatory cycles increased after exposure to bright compared to dim light (12 versus 6 cycles, Wilcoxon tied p = 0.034).Conclusions:Morning exposure to bright light in the follicular phase of the menstrual cycle stimulates the secretion of hypophyseal reproductive hormones, promotes ovary follicle growth, and increases ovulation rates in women with slightly lengthened menstrual cycles. This might be a promising method to overcome infertility.

Sleep, Circadian Rhythms, and Fertility

“…In the same study, but with use of a different protocol, both morning bright light and (to a lesser extent) evening bright light increased LH secretion in the follicular and luteal stages of the menstrual cycle [61]. Another investigation that exposed women in the follicular stage of the menstrual cycle to a 45-min light pulse soon after awakening found increased levels of prolactin, FSH, and LH [30]. Ovarian follicle size and number of ovulatory cycles also increased [30].…”

“…Another investigation that exposed women in the follicular stage of the menstrual cycle to a 45-min light pulse soon after awakening found increased levels of prolactin, FSH, and LH [30]. Ovarian follicle size and number of ovulatory cycles also increased [30]. Unfortunately, these studies were not designed to determine whether the impact of bright light on the ovulatory cycle is mediated by circadian phase shift, melatonin suppression, or changes in sleep.…”

Changes in European birth seasonality related to changes in regional sunshine

“…Therefore, it is not unreasonable that increased ELI might synchronize menstrual cycling or promote fertility. As previously noted, Danilenko and Samoilova (2007) have shown that bright morning light promotes human fertility and modulates the menstrual cycle. Because the specificity and accuracy of the ELI/PP prediction is in close agreement with a concurrent change in European sunshine, random coincidence seems unlikely.…”

“…Further support may be found in a recent study by Danilenko and Samoilova (2007) who conclude that bright light in the morning (4300 lux) in the follicular phase of the menstrual cycle stimulates the secretion of hypophyseal reproductive hormones, promotes ovary follicle growth, and increases ovulation rates in women with slightly lengthened menstrual cycles.…”

Biological rhythms and fertility: the hypothalamus&ndash;pituitary&ndash;ovary axis

“…36 This original report was supported and extended by findings that the menstrual cycle was shortened in 38 patients with winter depression after the daily exposure to light for 1 week as started between the days 1 and 14 of the menstrual cycle 99 and that exposure to sunshine 2 days or 3 days before the ovulation appears to shorten the men strual cycle. 100 Moreover, among women with lengthened menstrual cycles, the ovulation was promoted, the follicle size was increased, and the circulating levels of prolactin, LH, and FSH were increased by the daily exposure to bright light for 1 week between the days 7 and 14 of the menstrual cycle. 101 The effect of light on FSH secretion appears to be direct, mildly stimulating, and transient.…”