Andropause is caused by the reduction of hormones testosterone and dehydroepiandrosterone in middle-aged men. Late-onset hypogonadism is a rare condition in older men, characterized by measurably low testosterone levels and clinical symptoms mostly of a sexual nature, including decreased desire for sex, fewer spontaneous erections, and erectile dysfunction. It is the result of a gradual drop in testosterone; a steady decline in testosterone levels of about 1% per year can happen and is well documented in both men and women.
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