Post menopausal women taking HRT to manage hot flushes, osteoporosis and night sweats have now been warned that they risk progressive hearing loss between 15 and 21% if they have been on the hormone for 10 years.

Although they do not know the cause, scientists suspect a surge of the hormone from HRT could disrupt oestrogen receptors on the auditory hair cells located within the spiral organ of Corti. The study at Brigham and Women’s Hospital in Boston, Massachusetts, examined self-reported hearing loss in 80,792 post-menopausal women. Lead author Dr Sharon Curhan said that their study found hormone therapy use was associated with higher risk of hearing loss, and the risk tended to increase with duration of use. Oestrogen is known to affect hearing, with younger women actually less able to hear during the part of their menstrual cycle when the level of the hormone is lowest. Previous studies suggested the menopause may increase women’s risk of deafness – which led scientists to think that HRT could help.

The US research is the first large study looking at hearing loss and hormone therapy. Women, like men, lose their hearing as they age. But the study found those who had the menopause at an older age had a higher risk of hearing loss. This could be due to a longer exposure to oestrogen and progestogen during their lifetime.

A study last month showed HRT could protect against heart disease, with women in their fifties and sixties having a 30 per cent lower chance of dying over eight years. But the evidence differs over whether it raises the risk of some cancer. Dr Heather Currie, of the British Menopause Society, said: ‘This trial relies on self-reported hearing loss and does not prove that HRT causes this – only that there may be an association. This should not terrify women and the decision about HRT should be based on the balance of benefits and risks.’