The barrage of advertisements targets older men. “Have you noticed a recent deterioration of your ability to play sports?” “Do you have a decrease in sex drive?” “Do you have a lack of energy?”

If so, the ads warn, you should “talk to your doctor about whether you have low testosterone” — “Low T,” as they put it.

In the view of many physicians, that is in large part an invented condition. Last year, drug makers in the United States spent $3.47 billion on advertising directly to consumers, according to FiercePharma.com. And while ever-present ads like those from AbbVie Pharmaceuticals have buoyed sales of testosterone gels, that may be bad for patients as well as the United States’ $2.7 trillion annual health care bill, experts say.

Sales of prescription testosterone gels that are absorbed through the skin generated over $2 billion in American sales last year, a number that is expected to more than double by 2017. Abbott Laboratories — which owned AbbVie until Jan. 1 — spent $80 million advertising its version, AndroGel, last year.