Low testosterone, which can cause sexual dysfunction, loss of muscle mass, obesity, hair loss, and depression, may affect 30% of men who are overweight, compared to around 6% of those who are a healthy weight.

And around 35% of men with diabetes have low testosterone levels, compared to 12.6% of those without diabetes. Age is also a factor. About half of 80-year-old men contend with low-T.

That's not a surprise to researchers from the University of Western Australia. Their study, which appeared in the Annals of Internal Medicine, says older men can do a lot to influence how much testosterone deficiency they experience by making healthy lifestyle choices. Getting more than 75 minutes of vigorous exercise weekly; controlling high blood pressure; maintaining a healthy weight; and never smoking were all found to help maintain a healthy testosterone level.

What about taking medications to counter the drop?

Talk to your doctor about time-released testosterone, so you don't suffer permanent shutdown of your internal production of the hormone. And the biggest risk is blood clots, so ask about adding a daily low-dose aspirin to the regimen.

Women also need testosterone for healthy functioning, and a decline over time may lead to a decreased sex drive, depression, and muscle weakness.

Unfortunately, not a lot of research has been done on countering low testosterone’s impact on women. We do know smart lifestyle choices help, as can bioidentical estrogen patches (some estrogen is metabolized into testosterone).