From the article:
“Our study only looked at natural testosterone levels and so it doesn’t prove that testosterone supplements can prevent cognitive decline. We will need results of large randomized clinical trials in older men before we can confidently say that testosterone supplements are beneficial and safe,” she said.
Taking testosterone, or over-the-counter supplements that boost levels of the hormone, can have side effects including increased risk of prostate cancer, increased cholesterol levels, acne and male pattern baldness, Yaffe said.
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The cognitive tests measured concentration, memory, attention, language, and other cognitive skills. When scores on these tests decline significantly, or are well below average, this serves as a warning of a high risk of Alzheimer’s disease, Yaffe said.
In addition to testosterone, the researchers measured estrogen and sex hormone binding globulin, a protein that binds these two hormones. Although testosterone was linked to better scores on the tests, estrogen had essentially no effect on performance, Yaffe said. Previous studies of women have shown that higher estrogen levels can reduce their risk of cognitive decline.
Other research has shown that men have higher levels of both estrogen and testosterone than women, and that women have a 30 percent greater risk of developing Alzheimer’s Disease, Yaffe said. Some researchers hypothesize that women’s increased Alzheimer’s risk is related to lower hormone levels.
This study doesn’t explain how testosterone acts on the brain, Yaffe said, but other studies of mice have shown that the parts of the brain that handle learning and memory tasks are replete with receptors for testosterone.