Immediate effect of blue-enhanced light on reproductive hormones in women.

OBJECTIVE: Light is known to stimulate reproductive function in women. We here investigated the immediate effect of light on reproductive hormones, addressing the role of blue-sensitive (~480 nm) melanopsin-based photoreception mediating the non-visual effects of light. METHODS: Sixteen healthy women attended the Institute at ~07:25 (shortly after waking; sunglasses worn) twice in 2-3 days in April-May, within days 4-10 of their menstrual cycle. During one session, a broad-spectrum white-appearing light with a superimposed peak at 469 nm was presented against 5-10 lux background; during the other session, short-spectrum red light peaked at 651 nm with similar irradiance level (~7.0 W/m², corresponds to ~1200 lux) was used. Venous blood was taken at 0, 22 and 44 minutes of light exposure to measure concentrations of follicle-stimulating hormone (FSH), luteinising hormone (LH), prolactin, estradiol, progesterone and cortisol, and saliva was sampled to measure melatonin as a recognised indicator of the spectral-specific action of light. RESULTS: Melatonin values, as expected, were lower with white vs. red light (p=0.014), with the greatest difference at 22 minutes. Of the other hormones, only FSH concentrations differed significantly: they were mildly higher at white vs. red light (again, at 22 minutes; p=0.030; statistical analysis adjusted for menstrual cycle day and posture change [pre-sampling time seated]). CONCLUSION: Moderately bright blue-enhanced white light, compared to matched-by-irradiance red light, transiently (within 22 minutes) and mildly stimulated morning secretion of follicle-stimulating hormone in women in mid-to-late follicular phase of their menstrual cycle suggesting a direct functional link between the light and reproductive system.

Menstrual cycles are influenced by sunshine.

INTRODUCTION: The study determined the effect of seasons and meteorological variables on ovarian-menstrual function. METHODS: Women (N=129) living in Novosibirsk (55°N), Russia, provided data on normal menstrual cycles for over 1 year between 1999 and 2008. Of these, 18 together with 20 other healthy women were investigated once in winter and once in summer in 2006-2009. The investigated variables included serum levels of follicle-stimulating hormone (FSH), luteinising hormone (LH) and prolactin on day ∼ 7 of the menstrual cycle, ovary follicle size (by ultrasound) on day ∼ 12 and ovulation occurrence on subsequent days. RESULTS: In summer vs. winter, there was a trend towards increased FSH secretion, significantly larger ovarian follicle size, higher frequency of ovulation (97% vs. 71%) and a shorter menstrual cycle (by 0.9 days). LH and prolactin levels did not change. In all seasons combined, increased sunshine (data derived from local meteorological records) 2-3 days before the presumed ovulation day (calculated from the mean menstrual cycle) led to a shorter cycle length. Air/perceived temperature, atmospheric pressure, moon phase/light were not significant predictors. CONCLUSIONS: Ovarian activity is greater in summer vs. winter in women living in a continental climate at temperate latitudes; sunshine is a factor that influences menstrual cycle.