The National Institute of Neurological Disorders and Stroke says there is no reason to be alarmed about the long-term safety of medical testosterone therapy.
The agency says doctors can use the medication to help treat neuropathy and other chronic conditions that affect the nerve cells in the brain.
However, the news comes as a shock to patients who have been treated for decades with testosterone, which has been linked to long-lasting health problems, including infertility, bone loss and bone loss-related cancers.
In the U.S., there are no laws banning the medication, which is used for treating a wide range of medical conditions including chronic pain and depression.
But the news that testosterone is not a safe drug for medical use has brought concerns about its safety to a wider audience.
A study published in the journal Neurology found that while testosterone has been shown to be safe in animals, in humans it has a higher risk of side effects than the other common antidepressants.
It also found that the drug can lead to serious brain changes, including Alzheimer’s disease and Parkinson’s disease.
Some patients also say the medication can cause dizziness and headaches.
The news comes just weeks after an NIH study found that a small group of patients taking testosterone had more seizures than the general population.
“While the overall risk for severe neurological disease is low, it is possible that some people who take testosterone may have a lower risk than others,” said Dr. Paul J. Karp, the lead author of the study.
The drug is used to treat depression, Parkinson’s and anxiety disorders.
It has also been used for pain and to treat multiple sclerosis.
The NIH says the medication is not used for neuropathy, a condition that affects the nerve fibers in the spinal cord.
A 2013 study found there is an 80% chance of developing symptoms after taking testosterone.
“The most important consideration is to minimize the risk of adverse effects and to ensure that you are getting the appropriate amount of the drug for your condition,” the agency said in a statement.
A 2012 study found a single dose of testosterone, administered as a pill, had no significant effects on memory, attention or concentration.
However a second study found it had a greater effect on mood and memory.
In addition, it has been suggested that the treatment can cause other problems including increased blood pressure, headaches, depression, liver disease, and breast cancer.
The National Institutes of Health did not immediately respond to requests for comment on this story.
The New York Times first reported the news of the FDA’s warning.
A spokesperson for the FDA said the agency does not comment on ongoing investigations.
The report was published in an online edition of the journal Annals of Neurology, which was published earlier this month.
In its report, the FDA cites an article in The Lancet Neurology journal that linked testosterone to the increased risk of brain disease.
“There is no evidence that using testosterone for neuropathic pain is associated with a risk of developing or worsening neuropathic disease,” the FDA says.
However it notes that “there is no scientific evidence that the safety of testosterone therapy is enhanced by long-duration use.”
The FDA also notes that the company that makes the drug has received “a number of adverse events” from patients taking the medication.
The FDA has also said the drug “may increase the risk for other types of brain damage” including Alzheimer or Parkinson’s diseases.