It's much more common, he says, to treat low testosterone levels. A man's testosterone level peaks at age 20 and then slowly declines for the rest of his life. A problematic decrease can happen to men as early as their 30s, says Shippen. It's rare in the 30s, infrequent in the 40s, relatively common in the 50s and pretty common in the ages above. In short, says Shippen, the aging process accelerates.
Doctors can treat low testosterone levels with injections, patches and topical creams or gels.
A man on hormone replacement therapy will use it for the rest of his life, in the same way that women taking estrogen do. Once a man is on replacement therapy, it's important to monitor his testosterone levels, says Booth. A man may feel better at first, but if his levels get too high he could become aggressive and angry. In fact, monitoring testosterone levels every five years is a good idea for all men 35 or older, says Shippen. The reason to do testing in younger men periodically is to establish baseline levels when they're healthy.