The thyroid gland is found in the neck. It produces two hormones called thyroxine and triiodothyronine which affect a number of functions in the body such as heart rate. Hyperthyroidism is a condition where the thyroid gland becomes overactive and produces too much of these hormones, speeding up the body's processes.
Erectile dysfunction (ED), which is also known as impotence, is the inability to achieve and maintain an erection that is sufficient for sexual intercourse. ED is a common condition, affecting around one in 10 men. Older men are more likely to experience impotence.
The latest research led by teams from the University of Florence and the University of Manchester has demonstrated for the first time that hyperthyroidism can prevent a man attaining an erection. They say that as many as six out of 10 men with hyperthyroidism could encounter the problem.
The study, which appears in the International Journal of Andrology, investigated the relationship between thyroid hormones and erectile function in two large samples totalling 6,573 men in several European countries.
Testing for a link
The men were tested for thyroid stimulating hormone (TSH), which is responsible for controlling the production of thyroid hormones, and free thyroxine (FT4), the active form of the hormone thyroxine circulating in the blood.
From these, the researchers isolated 16 patients with hyperthyroidism.
In one of the groups tested, men with hyperthyroidism were 14 times more likely than their peers to suffer from erectile dysfunction, and 16 times more likely in the second group.
The authors say that men who develop problems getting an erection are not at higher risk of hyperthyroidism.
One of the lead researchers, Dr Giovanni Corona from the University of Florence, told BootsWebMD from a conference in Florence where he was presenting the study, that the findings suggest that erectile dysfunction was a direct result of hyperthyroidism "and not indirect action due to tiredness or other symptoms associated with the condition".
The authors say that further research is needed to investigate the effect that thyroid hormones have on the structure of the penis and to explore how thyroid therapy could affect sexual function.
Press release, European Society of Endocrinology.
'Thyroid hormones and male sexual function', G. Corona et al, International Journal of Andrology.
Dr Giovanni Corona, University of Florence.
'Thyroid, overactive', NHS Choices.
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