Aldosterone is good for hearing

[Guest guest]

Menopausal women with hearing loss may have low aldosterone and not

other hormone issues.

Source: University of Rochester Medical Center

Date: February 12, 2006

More on: Hearing Loss, Hearing Impairment, Disability, Healthy

Aging, Workplace Health, Diseases and Conditions

Hormone Linked To Good Hearing As We Age

Science Daily — Researchers have linked a hormone known to adjust

levels of key brain chemicals to the quality of our hearing as we

age. The more of the hormone that older people have in their

bloodstream, the better their hearing is, and the less of the

hormone, the worse their hearing is.

The hormone, aldosterone, is known to regulate kidney function and

also plays a role in controlling levels of two crucial signaling

chemicals in the nervous system, potassium and sodium. For nerves to

send signals crisply and work properly, potassium and sodium must be

in precise proportion, without any disruption in the molecular

channels or gates through which they move. Levels of potassium are

particularly crucial in the sensitive inner ear, where fluid rich in

potassium plays a central role in converting sounds into signals that

the nervous system recognizes.

The team of scientists in Rochester, N.Y., put 47 healthy men and

women between the ages of 58 and 84 through a battery of

sophisticated hearing tests. Scientists also measured their blood

levels of aldosterone, which is known to drop as people age. They

found that people with severe hearing loss had on average about half

as much aldosterone in their bloodstream as their counterparts with

normal hearing. The researchers noted, however, that the levels of

aldosterone found in all the participants is considered normal, and

that no patients or physicians should consider altering aldosterone

levels without more research.

The findings come from researchers at the International Center for

Hearing and Speech Research (ICHSR), a group funded by the National

Institute on Aging that is recognized as a leader in research on age-

related hearing loss. The center includes scientists from the

National Technical Institute for the Deaf at Rochester Institute of

Technology and neuroscientists from the University of Rochester.

" The inner ear is especially sensitive to any disruption in potassium

levels, " said D. Frisina, Ph.D., professor of Otolaryngology

at the University of Rochester Medical Center and an adjunct

professor at Rochester Institute of Technology. " We know that

potassium levels in the inner ear seem to decrease as we age and that

these falling levels play a role in age-related hearing loss, and we

also know that blood levels of aldosterone generally decrease with

age.

" We found a direct link between blood levels of aldosterone and the

ability of people to hear normally as they age. Depressed hormone

levels may hurt hearing both in the inner ear and the part of the

brain used for hearing. More research is needed, however, to

understand the precise role that aldosterone plays -- for instance,

whether it's a cause of failed hearing, or whether it's symptomatic.

Before we understand the issue more fully, people should not worry

about their aldosterone levels or look to boost the amount in their

bloodstream. "

The team led by Frisina published its results in the November issue

of the journal Hearing Research. This week at the annual

international meeting of the Association for Research in

Otolaryngology in Baltimore, the team presented its latest results

showing just how important potassium regulation is to age-related

hearing loss.

In Baltimore, Otolaryngology medical resident Spencer, M.D.,

presented results from " knockout " mice whose genes controlling the

potassium channels in the inner ear don't function properly, and

confirmed that malfunctioning potassium channels are central to age-

related hearing loss, or presbycusis. The channels are highly

concentrated in a part of the brain that plays an important role

providing feedback from the brain to the ears. Frisina's team

previously discovered that the feedback system is one of the first

things to go wrong in age-related hearing loss, often declining in

people who are in their 40s and 50s, usually before they even realize

their hearing is declining.

" We are now working out some of the underlying biology about how the

decline occurs, " said Frisina. " We have evidence that these potassium

channels may play an important role in the failure of the feedback

system, which is a big part of age-related hearing loss. "

Nearly everyone wrestles with failing hearing at some point. While

some people suffer from hearing damage as a result of exposure to

loud noise, or from other causes such as the side effects of some

medications, for many people hearing problems occur with no known

cause. Some people notice problems in their 40s and 50s, but the

process becomes very noticeable for most people in their 60s and

older.

Frisina said that until the biology of the problem is better

understood, the best advice for people concerned about hearing loss

is to limit exposure to loud, damaging noise and to medications that

are toxic to the ears. He also counsels people to eat healthy and to

exercise -- " all those things you know you should be doing to stay

healthy with age, " he said.

Meanwhile, his team is looking at the possibility of using gene

therapy to try to correct the problem. It may be possible some day to

modify a person's inner ear to correct the potassium imbalance that

is central to hearing loss. Such an approach might also address the

biggest cause of congenital deafness, which involves a genetic

mutation that mucks up the potassium balance in the inner ear.

The new findings come from a research group founded by

Frisina's father, D. Frisina, Ph.D., founding director of

NTID, who heads one of the largest research groups in the world

studying age-related hearing loss. The group has attracted top

researchers from around the world to come together to study the

problem. Members of the group, which numbers more than two dozen,

hail from Egypt, Brazil, Russia, China, Korea, India, and the United

States.

In addition to Frisina, Frisina and Spencer, the team includes post-

doctoral research associate Sherif Tadros, M.D., of both the

University and NTID, who is first author of the Hearing Research

paper; research nurse Frisina of both NTID and the University;

audiologist Frances Mapes of NTID; and otolaryngologist Xiaozia Zhu,

M.D., of the University.