Having high levels of testosterone could be dangerous for men, scientists fear.
Researchers found a natural abundance of the hormone in men is linked to blood clots, heart failure and heart attacks.
The findings also have implications for men who take testosterone supplements to boost energy levels and sex drive, the experts warned.
However, they were unable to prove whether testosterone directly causes the heart conditions - and have called for further trials.
Researchers at the City University of New York and the University of Hong Kong led the study, published in the British Medical Journal.
They analysed data from 400,000 men and women, aged 40 to 75 years, from an existing study and the UK Biobank database.
The study team, led by Professor Mary Schooling, assessed the genes that predict testosterone levels and their links to heart problems.
Heart conditions were identified from self-reports, hospital and death records, and results were validated using data from another large study.
The researchers found that in men, high natural testosterone was clearly associated with a higher risk of blood clots, heart failure and heart attack.
The same associations were far less obvious in women, who have very low levels of testosterone.
The researchers concluded testosterone 'is detrimental for thromboembolism, heart failure, and myocardial infarction, especially in men'.
And they say further evidence is needed to clarify whether the findings are relevant to the higher rates of these diseases in men than in women.
They also suggest that it may be worth considering whether existing treatments that lower testosterone could help protect against these conditions.
Some 69,000 women have a heart attack in the UK every year, compared to 119,000 men, according to statistics.