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If testosterone levels are low, a man may feel blue, tired or irritable. He may have lower sexual desire and decreased confidence. He may be mentally sluggish. In such cases, testosterone treatment may help.

Hormone production tends to fall off gradually after age 40. Only 1 in 100 men under 40 have low testosterone. By age 70, a man on average produces about half as much as he did in his 20s. But for most men, that level is still considered normal.

That’s why it’s hard to define what low means. Hormone levels fall in every man as he ages. After 50, this decline can contribute to depression symptoms. Drinking, being overweight and stress can make the problem worse. But if depression is severe, it’s less likely to be due to low testosterone.

You may have heard the term “male menopause.” That name’s misleading. Men continue to make testosterone. They don’t go through a sudden change the way women do with estrogen.

Your doctor will not only check testosterone. He or she will do a complete medical exam. And may suggest other tests. If the level is in the normal range, the doctor will probably not recommend this treatment.

Moreover, because of potential side effects, testosterone treatment should never be taken lightly. It is not an anti-aging pill.

Extra testosterone may increase the risk of prostate cancer. It can boost the level of “bad” cholesterol. In some cases, extra testosterone may be bad for your liver or heart. Other side effects are breast swelling, headache, rash, acne, or baldness. And just what you don’t want — testosterone can sometimes make you feel worse rather than better emotionally.

Still, testosterone treatment can bring a low level up to the normal range. The prescription is often a gel or a patch placed on the skin. It can also be given in an injection every other week. Depending on the circumstances, the doctor may suggest psychotherapy or an antidepressant drug, or both.