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Researchers may have discovered a way to reverse one type of hearing loss.
A new study found that hearing loss caused by mutations in a certain gene at birth may be reversed by a common supplement along with the erectile dysfunction drug Viagra (sildenafil).
Researchers identified mutations in a gene known as CPD — which produces the enzyme carboxypeptidase D — among three unrelated families from Turkey in which multiple people were born deaf.
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These families all had a form of inherited sensorineural hearing loss, a condition caused by damage to the tiny hair cells in the inner ear that convert sound vibrations into electrical signals sent to the brain, according to the National Institutes of Health.
To better understand the link, the scientists compared the genetic data of affected and unaffected relatives within these families. They then expanded their analysis to other groups.
"We subsequently found that CPD mutations are present in people with hearing loss in a large genome sequencing cohort from England," study author Dr. Mustafa Tekin, professor of human genetics and chair of Department of Human Genetics at University of Miami Miller School of Medicine, told Fox News Digital.
After turning the CPD gene "off" in human cells in laboratory tests, the researchers noted reduced levels of three substances: arginine (an amino acid), cyclic guanosine monophosphate (cGMP, an important signaling molecule) and nitric oxide, which provides vital signals to the nervous system.
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Although the study began with humans, the reversal experiments were also carried out in mice and fruit flies.
When nitric oxide and cGMP levels were low, the hair cells in the mice’s inner ears — which transmit sound signals to the brain — became overstressed and eventually died.
In fruit flies, researchers found that silencing the equivalent of the CPD gene led to defects in the organ that helps them detect sound and stay balanced.
But when the researchers administered arginine to human cells, nitric oxide levels returned to normal, resulting in fewer cells dying.
They also found that Viagra, which acts on the nitric oxide pathway, reversed some of the deficits caused by CPD mutations, Tekin added.
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These findings suggest that nitric oxide deficiency in the cochlea — the part of the inner ear that converts sound vibrations into nerve signals — may be a key driver of hearing loss. The CPD gene appears to regulate this process by maintaining proper arginine and nitric oxide levels in hair cells, which are essential for healthy signal transmission and protection against noise-related damage.
"Nitric oxide is vital for many tissues and must be kept in a fine balance," Tekin said.
The authors emphasized, however, that they are not proposing Viagra as a hearing loss treatment.
"We used it to strengthen the argument that nitric oxide deficiency in the ear was the underlying cause of deafness," Tekin noted.
Outside experts also warned of an important adverse side effect of Viagra.
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The medication has been associated with rare but serious cases of sudden hearing loss as well as irreversible tinnitus, underscoring the need for caution, Dr. Nooshin Parhizkar, an ENT physician practicing in the San Francisco Bay Area, told Fox News Digital.
"At this stage, it is not appropriate or safe for the general public to use Viagra for hearing issues," she added.
The hearing loss is usually temporary and reversible after stopping the medication, research has shown.
The Food and Drug Administration added a warning label to Viagra and other PDE5 inhibitors about the possible risk of sudden hearing loss after rare reports among those who used the same class of medication.
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It’s unclear whether this side effect is directly caused by the PDE5 inhibitors, as the affected patients may have other medical issues or could be taking other medications that could have led to the hearing loss, according to experts.
The study focused on a very small, genetically defined group of patients, so it is unlikely to apply to most of the population, Parhizkar pointed out.
As the research also focused on reversing hearing loss in mice and flies, more studies are needed to evaluate treatment in humans.
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"It is important to get a genetic test done to find the cause of hearing loss," Tekin advised.
Although scientists have identified more than 200 genes linked to hearing loss, commercial genetic screening tests may only focus on the most common mutations.
Fox News Digital reached out to the maker of Viagra for comment.
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