Heart attacks did not rise on testosterone; three other problems did
In 5246 men with heart disease or high risk, major cardiac events ran 7.0% against 7.3% on placebo. Irregular heartbeat, kidney injury and lung clots each ran higher. The makers funded it.
What the study found
Major cardiac events did not rise; three other events did
In 5246 men with low testosterone and existing heart disease or high risk of it, testosterone gel produced major cardiac events in 7.0% against 7.3% on placebo, clearing the noninferiority margin. Irregular heartbeat, kidney injury and clots in the lung were each more common on it.
The caveat · Not worse than placebo is not safe
Noninferiority means testosterone was not worse than placebo by more than a preset margin, which is a different statement from safe. The three excess events were not adjusted for multiple comparisons and the trial was not powered to find them. Doses were titrated into the low-to-mid normal range, so nothing here speaks to higher amounts. The trial was funded by testosterone manufacturers.
What we don't know
Whether testosterone harms the arteries is unresolved. The largest trial found no rise in major cardiac events; an imaging trial found more non-calcified plaque after a year. Nobody has shown whether that plaque turns into events.