Light exposure might serve some of the same functions for which people take testosterone and other androgens, according to researchers at the University of California, San Diego (UCSD) School of Medicine. Researchers found that the levels of a pituitary hormone called luteinizing hormone (LH), which increases testosterone, are enhanced after exposure to bright light in the early morning.
The finding supports data that bright light can trigger ovulation in women, which is also controlled by LH, according to one of the study's authors, Daniel Kripke, M.D., UCSD professor of psychiatry. The study involved 11 men between the ages of 19 and 30 years. They were exposed to bright light (1,000 lux) from 5 a.m. to 6 a.m. for five days and then to a placebo light for five days. The men's LH excretion was measured after the exposures.
Researchers found that LH levels increased 69.5 percent after bright light exposure in the early morning. Levels of the hormone melatonin, which increases at night and is inhibited by light, were also measured. While animal
studies have suggested that melatonin might restrain the effects of light on LH, the current study found no such association.
It has also been found in previous studies conducted by the Kripke group and others that bright light exposure helps alleviate the symptoms of depression, such as sexual dysfunction. Depressive symptoms such as loss of libido and decreased sexual activity, which are also known side effects of newly developed antidepressant drugs, may be helped by bright light exposure, according to the study's authors.
Neuroscience Letters (341, 2003, 25-28) April 16, 2003
Dr. Kaniel Kripke website: http://www.brightenyourlife.info
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