Luteinizing hormone following light exposure in healthy young men (original) (raw)
Related papers
Weak evidence of bright light effects on human LH and FSH
Journal of Circadian Rhythms, 2010
Background: Most mammals are seasonal breeders whose gonads grow to anticipate reproduction in the spring and summer. As day length increases, secretion increases for two gonadotropins, luteinizing hormone (LH) and follicle stimulating hormone (FSH). This response is largely controlled by light. Light effects on gonadotropins are mediated through effects on the suprachiasmatic nucleus and responses of the circadian system. There is some evidence that seasonal breeding in humans is regulated by similar mechanisms, and that light stimulates LH secretion, but primate responses seem complex.
The effect of dim light on suppression of nocturnal melatonin in healthy women and men
Journal of Neural Transmission, 1997
The present study investigated the effect of dim white light on nocturnal plasma melatonin in males and females. Subjects were exposed to light between 2400hr and 0100hr. No significant gender differences were found with both 2001ux (p > 0.1) and 5001ux (p > 0.1) of light. Furthermore the amplitude of the melatonin rhythm was not significantly different with gender. This suggests that at low intensities the melatonin sensitivity to light is not differentially regulated between sexes.
International Journal of Molecular Sciences
Artificial light at night can have negative effects on human wellbeing and health. It can disrupt circadian rhythms, interfere with sleep, and participate in the progress of civilisation diseases. The aim of the present study was to explore if dim artificial light during the entire night (ALAN) can affect melatonin production and sleep quality in young volunteers. We performed two experiments in real-life home-based conditions. Young volunteers (n = 33) were exposed to four nights of one lux ALAN or two nights of five lux ALAN. Melatonin production, based on 6-sulphatoxymelatonin/creatinine concentrations in urine, and sleep quality, based on actimetry, were evaluated. Exposure to ALAN one lux during the entire night did not suppress aMT6s/creatinine concentrations but did aggravate sleep quality by increasing sleep fragmentation and one-minute immobility. ALAN up to five lux reduced melatonin biosynthesis significantly and interfered with sleep quality, as evidenced by an increased...
Journal of Biological Rhythms, 2019
The human circadian system is primarily regulated by the 24-h LD cycle incident on the retina, and nocturnal melatonin suppression is a primary outcome measure for characterizing the biological clock’s response to those light exposures. A limited amount of data related to the combined effects of light level, spectrum, and exposure duration on nocturnal melatonin suppression has impeded the development of circadian-effective lighting recommendations and light-treatment methods. The study’s primary goal was to measure nocturnal melatonin suppression for a wide range of light levels (40 to 1000 lux), 2 white light spectra (2700 K and 6500 K), and an extended range of nighttime light exposure durations (0.5 to 3.0 h). The study’s second purpose was to examine whether differences existed between adolescents’ and adults’ circadian sensitivity to these lighting characteristics. The third purpose was to provide an estimate of the absolute threshold for the impact of light on acute melatonin...
Medical Hypotheses, 2004
The hypothesis that the suppression of melatonin (MLT) by exposure to light at night (LAN) may be one reason for the higher rates of breast and colorectal cancers in the developed world deserves more attention. The literature supports raising this subject for awareness as a growing public health issue. Evidence now exists that indirectly links exposures to LAN to human breast and colorectal cancers in shift workers. The hypothesis begs an even larger question: has medical science overlooked the suppression of MLT by LAN as a contributor to the overall incidence of cancer? The indirect linkage of breast cancer to LAN is further supported by laboratory rat experiments by David E. Blask and colleagues. Experiments involved the implanting of human MCF-7 breast cancer cell xenografts into the groins of rats and measurements were made of cancer cell growth rates, the uptake of Linoleic Acid (LA), and MLT levels. One group of implanted rats were placed in light-dark (12L: 12D) and a second group in light-light (12L:12L) environments. Constant light suppressed MLT, increased cancer cell growth rates, and increased LA uptake into cancer cells. The opposite was seen in the light-dark group. The proposed mechanism is the suppression of nocturnal MLT by exposure to LAN and subsequent lack of protection by MLT on cancer cell receptor sites which allows the uptake of LA which in turn enhances the growth of cancer cells. MLT is a protective, oncostatic hormone and strong antioxidant having evolved in all plants and animals over the millennia. In vertebrates, MLT is normally produced by the pineal gland during the early morning hours of darkness, even in nocturnal animals, and is suppressed by exposure to LAN. Daily entrainment of the human circadian clock is important for good human health. These studies suggest that the proper use and color of indoor and outdoor lighting is important to the health of both
Neuroscience Letters, 1997
Effects of bright light exposure at midday were examined on plasma melatonin rhythm in humans under controlled living conditions. Bright light of 5000 lx was provided from the ceiling at midday (1100-1700 h) for 3 consecutive days and the circadian rhythm in plasma melatonin was determined from the fourth to fifth day. The control study was performed in the same subjects who spend four days under dim light conditions (less than 200 lx). The subjects were allowed to sleep from 2400 to 0800 h. The onset phase, but not the end phase, of plasma melatonin rhythm was significantly phase-advanced by bright light exposure. Furthermore, the area under the curve of nocturnal melatonin rise was significantly larger under bright light exposure than under dim light. These findings indicate that midday exposure to bright light for 3 consecutive days changes the circadian organization of plasma melatonin rhythm in humans.
European Journal of Endocrinology, 1994
Lemmer B, Brühl T, Witte K, Pflug B, Köhler W, Touitou Y. Effects of bright light on circadian patterns of cyclic adenosine monophosphate, melatonin and cortisol in healthy subjects. Eur J Endocrinol 1994; 130:472–7. ISSN 0804–4643 Bright light is known as a strong zeitgeber on human circadian rhythms and influences several endocrine and neuroendocrine functions. In the present study we examined the influence of a 3-h bright light stimulus, given at different times during the day (morning or evening), on circadian patterns of cyclic adenosine monophosphate (cAMP), melatonin and cortisol. Two groups of synchronized healthy volunteers (lights on: 05.00–23.00 h) were exposed to bright light (2500 lux) for 3 h over 6 days either in the morning (05.00–08.00 h) or in the evening (18.00–21.00 h). The results showed a significant phase advance in the circadian rhythms of melatonin and cortisol when bright light was given in the morning but not when given in the evening. Rhythm in plasma cAM...
Biomedical Journal, 2016
Background: Continuous light or darkness has various effects on different systems. In the present research work, the effects of constant light and darkness exposure of male rats and oral administration of exogenous melatonin on the serum levels of melatonin have been studied. Methods: Thirty adult male Wistar rats were divided into six groups of: (1) Control, (2) melatonin, (3) light, (4) light and melatonin, (5) darkness, and (6) darkness and melatonin. All groups were placed according to light conditions for 10 days. Melatonin was administered orally after a period of 10 days to Groups 2, 4, and 6 (10 mg/kg of body weight). Serum levels of melatonin were measured using ELISA. Results: The results showed the significant difference on serum melatonin in darkness, no light, and control groups. Although serum levels of melatonin were different in melatonin groups, the difference is not significant. Conclusions: We concluded that being exposed to continuous darkness leads to an increase in serum melatonin.
Melatonin effects on luteinizing hormone in postmenopausal women: a pilot clinical trial NCT00288262
BMC women's health, 2006
In many mammals, the duration of the nocturnal melatonin elevation regulates seasonal changes in reproductive hormones such as luteinizing hormone (LH). Melatonin's effects on human reproductive endocrinology are uncertain. It is thought that the same hypothalamic pulse generator may both trigger the pulsatile release of GnRH and LH and also cause hot flashes. Thus, if melatonin suppressed this pulse generator in postmenopausal women, it might moderate hot flashes. This clinical trial tested the hypothesis that melatonin could suppress LH and relieve hot flashes. Twenty postmenopausal women troubled by hot flashes underwent one week of baseline observation followed by 4 weeks of a randomized controlled trial of melatonin or matched placebo. The three randomized treatments were melatonin 0.5 mg 2.5-3 hours before bedtime, melatonin 0.5 mg upon morning awakening, or placebo capsules. Twelve of the women were admitted to the GCRC at baseline and at the end of randomized treatment f...
Journal of Molecular Neuroscience, 1999
The role of melatonin in the regulation of human reproduction remains unclear. In the present study, we examined the influence of exogenous melatonin on pulsatile luteinizing hormone (LH), diurnal rhythm of testosterone, and endogenous melatonin profile in six healthy young adult males. To test the hypothesis that the effect of melatonin on LH or testosterone secretory patterns may be mediated through the benzodiazepine-(BNZ) γ-amino-butyric acid (GABA) receptor complex, a benzodiazepine receptor antagonist (Flumazenil) was administered. The study design comprised four 10-h (4:00 PM-2:00 AM) testing periods. During each experimental period, subjects were given an oral dose of placebo, or 3 mg melatonin or 10 mg flumazenil, at 5:00 PM, in a randomized, double-blind, partially repeated Latin square design in the following combinations: placebo-placebo, placebo-melatonin, flumazenil-placebo, and flumazenil-melatonin. The following day, serum samples were obtained every 20 min between 4:00 PM and 2:00 AM in a controlled light-dark environment for the determination of LH and melatonin levels. Serum testosterone concentrations were determined every 20 min between 7:00 and 8:00 AM and 7:00 and 8:00 PM. A significant decrease in mean serum LH levels (p < 0.02) was observed in the melatonin-treated groups as compared with placebo-flumazenil groups. There was no change in LH pulse frequency, testosterone levels, or in melatonin onset time and amplitude. No additional effect of flumazenil on LH or testosterone levels was observed.