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Heart Health

13 November 2019

How testosterone supplements could double men's odds for blood clots

The findings of a new study suggest that men think twice about asking for testosterone treatments to battle normal symptoms of ageing.

Testosterone therapy appears to double a man's risk of suffering a potentially life-threatening blood clot, a new study warns.

Men had twice the risk for a deep vein blood clot if they'd been receiving testosterone during the previous six months, researchers reported in JAMA Internal Medicine.

Symptoms of ageing

The increased risk occurred whether or not a man had the low-testosterone condition known as hypogonadism, but appeared to be more pronounced in middle-aged men than in seniors, the findings showed.

These findings should cause men to think twice about asking for testosterone treatments to battle normal symptoms of ageing, said lead author Rob Walker, a graduate research assistant at the University of Minnesota School of Public Health, in Minneapolis.

"If a potential patient reads this and maybe is seeking out testosterone therapy for some kind of common symptoms, like weight gain or sexual function, maybe they should seek out behavioural changes or lifestyle changes that will improve their health without a prescription," Walker said.

The "low-T" fad caused testosterone prescriptions to soar early in the 21st century, increasing more than 300% between 2001 and 2013, the study authors said in background notes.

The fad faded in 2014, after the US Food and Drug Administration warned that testosterone therapy increases a man's risk of heart attack and stroke.

Deep vein clot

Still, more than one million US men over 30 received testosterone therapy in 2016, the researchers noted. Evidence suggests it's still being prescribed to some who don't suffer hypogonadism, a condition in which the body isn't producing enough of the male hormone.

To further investigate the risk of testosterone treatment, Walker and his team analysed insurance claims for nearly 40 000 men filed between 2011 and 2017.

The investigators focused on men who experienced either deep vein thrombosis or pulmonary embolism. Pulmonary embolism occurs when a deep vein clot breaks free and travels into the lungs, blocking some or all of their blood supply.

Men without a low-testosterone condition who took the hormone had 2.3 times the risk of developing a deep vein clot within six months, the results showed. Men diagnosed with hypogonadism had two times the risk.

The results also indicated that risk might be even greater in middle-aged men taking testosterone to battle ageing, although those findings were not statistically significant, Walker said.

Sluggish blood flow

"In men without hypogonadism, men under 65 almost had a tripling of risk versus men 65 years and older, whose risk was only about 1.5 times greater," he said.

Testosterone poses this risk because it "revs up the consistency of the clotting factors in the blood", said Dr Umesh Gidwani, an associate professor of cardiology, critical care and pulmonology at the Icahn School of Medicine at Mount Sinai in New York City.

The hormone increases red blood cell count, which thickens blood and makes it flow more sluggishly, Gidwani said. Testosterone also amps up the action of platelets, the blood cells responsible for forming clots.

The study "seems to suggest it would be safer to refrain from testosterone use in patients who do not have hypogonadism," Gidwani said.

Walker agreed, adding that men who must receive testosterone therapy due to hypogonadism should be closely monitored for blood clots.

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