Positive data on T products follow blood clot warning

Testosterone replacement therapy is in the news again, for reasons both good and bad.

First, the bad-or at least cautionary-news: Last week, the FDA issued a statement saying it is requiring manufacturers to include a general warning in the drug labeling of all approved testosterone products about the risk of venous blood clots, even in patients without polycythemia.

“The risk of venous blood clots is already included in the labeling of testosterone products as a possible consequence of polycythemia… Because there have been postmarket reports of venous blood clots unrelated to polycythemia, FDA is requiring a change to drug labeling of all testosterone products to provide a more general warning regarding venous blood clots and to ensure this risk is described consistently in the labeling of all approved testosterone products,” the statement said.

The FDA added that this warning is unrelated to the organization’s previously announced evaluation of the possible risk of stroke, heart attack, and death in patients taking testosterone products.

It hasn’t all been bad for testosterone lately, however, as indicated by two studies reported at the joint meeting of the International Society of Endocrinology and the Endocrine Society in Chicago. U.S. researchers reported that testosterone replacement therapy might help mobility-limited older men improve and maintain aerobic capacity, and Australian researchers found declining physical function to be twice as common in older men with low testosterone or other hormone levels compared with those with the highest levels.

In the U.S. study, researchers analyzed data from a larger randomized controlled study of men over 65 years of age who had low testosterone levels and had difficulty performing everyday physical activities. For 6 months, men in one group received 10 mg of a testosterone gel, while men in a second group received a placebo gel. All participants completed a cycle exercise test to measure peak aerobic fitness before and after the study.

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The men in the testosterone group showed a slight improvement in aerobic fitness, while the placebo group showed a slight decline.

"These findings are potentially relevant to older men who have experienced the age-related decline in endurance capacity that may be due in part to low testosterone. If proven safe over the long-term, restoring testosterone to normal levels may improve an important measure of physical performance and enhance their quality of life," said study author Thomas W. Storer, PhD, of Brigham and Women’s Hospital of Harvard Medical School in Boston.

In the second study, Australian researchers evaluated 1,318 men 70 years of age and older who had health assessments between 2005 and 2007 and again 2 years later. The men reported their ability to perform activities such as walking, eating, getting dressed, and personal hygiene. They also had blood tests that measured hormones such as testosterone, dihydrotestosterone, estradiol, and estrone.

The authors reported that elderly men with low levels of testosterone or other sex hormones were twice as likely to have declining physical function over 2 years’ time compared with elderly men who have the highest hormone levels.

“We also found that increasing muscle weakness-possibly due to decreasing testosterone concentration in the blood-could explain most of this relationship,” said principal investigator Benjamin Hsu, MPH, of the University of Sydney.

Both studies come closely on the heels of the approvals of the topical testosterone gel Vogelxo and the testosterone nasal gel Natesto. Earlier this month, Auxilium Pharmaceuticals said it is partnering with Prasco, LLC to introduce a generic version of Testim, also a testosterone gel.