A popular form of hormone replacement therapy (HRT), which is often used to stave off the changes associated with female aging, can accelerate hearing loss. University of Rochester researchers led by Robert D. Frisina found that women who were taking a combination of estrogen and progestin had hearing deficits typically expected in women five to 10 years older. The study of 124 women between the ages of 60 and 86 points to progestin as the culprit, because the hearing of participants who took estrogen alone was unaffected by the treatment.
Previous studies have also documented slight hearing loss in women taking birth-control pills containing progestin and in younger women during the stage of their menstrual cycles when progesterone, the hormone's natural form, is at its highest level. Yet women still have better overall hearing than men up until menopause, a benefit attributed to natural estrogen.
Frisina thinks that the progestin-induced damage detected in the study may arise when nerve cell membranes are exposed to a progestin metabolite, allopregnanolone: the cells become less excitable, or responsive, to stimulation. If that is the mechanism at work, then the nerve cells in the HRT group with hearing loss may be dampened but not dead, suggesting that the effect is reversible. Frisina's group plans to study next what happens to women's hearing when they stop HRT.
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Frisina would like to see drug companies perform similar sensory testing during development of HRT products and release any results they may already have. “It might be valuable information,” he says. In the meantime, the hearing risk “should be part of the conversation when a woman and her doctor discuss HRT,” he adds, particularly for women who already have hearing loss.