Progestin, a synthetic version of the hormone progesterone, increases hearing loss, according to new research.
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SYDNEY, 11 September 2006: Women who take the most popular form of hormone replacement therapy after they have reached menopause may suffer premature hearing loss, a new study suggests.
Birth control pills also contain the synthetic hormone in question, progestin, prompting researchers to call for further investigation.
Scientists compared the hearing of 124 healthy post-menopausal women, ranging in age from 60 to 86. Women taking HRT containing progestin were 10 to 30 percent deafer than women who had not taken the treatment, according to the study, published last week by the U.S. journal, Proceedings of the National Academy of Sciences.
"Whether a woman goes on HRT is certainly her decision, and she should discuss the options with her doctor," said senior author Robert Frisina, a neuroscientist from the University of Rochester Medical Centre.
"In light of these findings, we feel that hearing loss should be added to the list of negative things to keep in mind when talking about HRT. Women especially who already have a hearing problem should weigh this decision carefully. Women on HRT should consider having a thorough hearing check-up done every six months."
Researchers at the International Centre for Hearing and Speech Research administered four types of hearing tests to the women, who were split into three groups. Thirty of the women had taken HRT with oestrogen alone; 32 women had taken HRT with oestrogen and progestin and 62 had never taken any form of HRT. The women from each group were matched by age and health.
The first test was a standard pure-tone test, where women raised their hands when they heard a tone, indicating what range of frequencies they can hear. The women also underwent two middle-ear tests, measuring how the eardrum reacts to changes in air pressure produced by different sounds. The women also took a hearing-in-noise test to determine their ability to distinguish speech from other noises.
Across the board, results from the tests showed that women who had taken HRT with progestin had the worst hearing. The progestin group had problems in the inner ear and parts of the brain used for hearing, said the study.
The group also predicted that HRT with only oestrogen would have a protective effect on hearing due to the results suggested in previous studies. However, the results of the current study showed that oestrogen yielded no hearing benefits, according to the paper.
"It's long been thought that oestrogen is good for nerve cells so we wanted to see if women on oestrogen as part of HRT had better hearing than women not on HRT," said Frisina. "We were very surprised to find not only that women on oestrogen did not hear better than other women, but that the women who were also on progestin actually heard worse."
The team plans to continue its research to try to find out the "exact effects" of progestin on the ears and brain and hope to investigate the role of progestin in the birth control pill.
They would also like to study women who have stopped taking HRT, to see if the hearing problems are reversible.
