IF YOU CONSTANTLY feel down in the mouth, and even meds or watching Jennifer Garner whup ass in slinky, skin-tight outfits doesn’t seem to help, check your testicles. According to a new study published in the American Journal of Psychiatry, men suffering from depression may benefit from testosterone replacement therapy. When researchers at McLean Hospital in Belmont, Mass., tested 54 men whose symptoms weren’t relieved by antidepressant drugs, they found that 43% of them had low testosterone levels. Those who received a testosterone gel for eight weeks showed significant improvement in mood, sleep, appetite and libido.

IF YOU BELIEVE you may have low testosterone levels, you should see a doctor. Keep in mind that hormone replacement can cause side effects, such as putting you at greater risk for prostate enlargement, making a PSA (prostate-specific antigen) screening mandatory prior to beginning therapy. But if your doctor finds you have “low-normal” levels and you want to increase them without taking supplements, try the following:

* If you’re overweight, lose that excess body fat. Exercise, eat healthful foods and decrease portion sizes, but don’t cut out protein or healthy fats–that will only make your testosterone problem worse.

* Get at least eight hours of sleep every night. That’s when your body’s hormone factory is at peak production.

* Make sure you’re getting enough zinc. The Recommended Daily Allowance is 15 milligrams, but you may need more if you work out regularly.

* Alcohol and testosterone don’t mix, so cut back on R-rated beverages.

* Practice stress-reduction techniques such as meditation, deep breathing and yoga.

* Do weightlifting workouts at least three times per week. Research at Ball State University in Muncie, Ind., found that multiset exercises are best for boosting testosterone, especially when you follow the workout with a protein/ carbohydrate supplement.