In recent years, makers of prescription testosterone treatments like AndroGel began throwing around the term “Low T” in TV ads, blaming low levels of the hormone for various problems — sex drive, flagging energy, moodiness — that have long been associated with simply growing older. But the FDA is now acknowledging that these drugs pose “a possible increased risk of heart attack and stroke” and are warning against their use for the treatment of anything other than very specific medical conditions.

Prescription testosterone is only FDA-approved for men with low testosterone levels due to disorders of the testicles, pituitary gland, or brain that cause a condition called hypogonadism.

But in an announcement made Tuesday afternoon, FDA notes that “testosterone is being used extensively in attempts to relieve symptoms in men who have low testosterone for no apparent reason other than aging.”

Citing the possible increased cardiovascular risk, FDA is requiring labeling changes for all prescription testosterone products to “reflect the possible increased risk of heart attacks and strokes associated with testosterone use.”

The agency is asking doctors and other health care professionals to alert patients of the risks associated with testosterone. Patients using testosterone should seek medical attention immediately if symptoms of a heart attack or stroke are present, such as: chest pain, shortness of breath or trouble breathing, weakness in one part or one side of the body, or slurred speech.

“We are also requiring manufacturers of approved testosterone products to conduct a well-designed clinical trial to more clearly address the question of whether an increased risk of heart attack or stroke exists among users of these products,” reads the announcement.

The FDA first announced that it was investigating the potential cardiovascular risks of these gels in Jan. 2014 after two studies raised safety questions.

The first study, published in 2013 in the Journal of American Medical Association, looked at a group of men (average age: 60) with low serum testosterone. The results of the research indicated that men undergoing testosterone treatment may be at a 30% increased risk of stroke, heart attack, and death.

A second study observed an increased risk of heart attack in both older men and in younger men with pre-existing heart disease, who filled a prescription for testosterone therapy. For men over the age of 65 who were being treated with testosterone, researchers claimed a twofold increase in the risk of heart attack in the first 90 days after beginning treatment. For younger men with a pre-existing history of heart disease, the study found a two- to threefold increased risk of heart attack in the first 90 days. The study did not see any increased risk for heart attack in younger men.

In Feb. 2014, health safety advocates at Public Citizen petitioned the FDA for a “black box” warning on testosterone packaging about cardiovascular risks, or at least a patient medication guide. In June 2014, FDA rejected the petition, claiming “insufficient evidence.”

Around the same time, regulators in Canada concluded that studies on testosterone treatments “provide evidence in support of this possible association when considered as a whole.”

“In the seven and a half months since the Canadian action, approximately four million [testosterone] prescriptions have been filled in the U.S.,” reads a statement from Public Citizen. “Had the FDA made this announcement last summer when the Canadian government acted, it would have reduced the number of U.S. prescriptions for and damage from testosterone, a medication of questionable effectiveness for a large proportion of users and one that increases the risk of heart attacks and strokes.”

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