Chicago - A steep decline in levels of the hormone testosterone can trigger depression in some older men, researchers said on Monday.
While most men's testosterone levels decline gradually after age 40, a severe drop called hypogonadism afflicts roughly 30 percent of men over age 55.
The condition can cause decreased muscle mass and strength, less bone mineral density, diminished appetite, decreased libido, fatigue and irritability.
"Hypogonadal men showed an increased incidence of depressive illness" in the study of 278 men older than 44, wrote study author Molly Shores of Veterans Affairs Puget Sound Health Care System, Seattle.
Shores said 22 percent of the men with hypogonadism were diagnosed with depression over a two-year period, against seven percent of those without the condition.
Testosterone levels normally peak in early adulthood, and then decrease by approximately one percent a year after age 40.
The study appeared in the journal Archives of General Psychiatry.