Bright Light May Boost Testosterone

Light Therapy Might Ease Sexual Dysfunction

April 22, 2003 -- Waking up to bright light may trigger a rise in male hormones that could ease sexual dysfunction and other symptoms of depression. A new shows that early morning light therapy caused a surge in a pituitary hormone called luteinizing hormone (LH) that raises testosterone levels in men.

Previous studies have shown that bright light therapy of daily exposure to specially designed, high-intensity light boxes can alleviate many symptoms of depression, especially among people who suffer from seasonal affective disorder (SAD) during winter months.

Researchers say sexual dysfunction, including loss of libido and decreased sexual activity, are commonly reported symptoms among people with depression as well as frequent side effects of antidepressant medications.

In this study, published in the current edition of Neuroscience Letters, researchers examined levels of LH following one hour of bright light therapy (1,000 lux) from 5-6 a.m. for five days in a row among 11 healthy men ages 19-30. The same group also was exposed to a placebo light (less than 10 lux) over a similar period.

Researchers found that LH levels increased by 69.5% after bright light therapy, but those levels were unchanged after placebo light exposure.

The study also looked at whether levels of the hormone melatonin, which rises at night and is thought to play a role in the natural sleep cycle, might be affected by light therapy. Previous studies in animals had suggested that melatonin might interfere with a light therapy-induced LH boost, but researchers found no evidence of this effect in humans.

Researcher In-Young Yoong, MD, PhD, who conducted the study at the University of California, San Diego, and colleagues say their findings suggest bright light therapy may not only ease sexual dysfunction in men, but it may also trigger ovulation in women, which is also controlled by LH.

Researchers say future studies should look at the effect of light therapy on LH levels in depressed people to see if it has the same hormone-raising effect found in these healthy volunteers.

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SOURCES: Neuroscience Letters, 341, 2003. News release, University of California, San Diego.
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