Men who get a low reading when tested for blood levels of testosterone should be retested after they fast overnight because sugar can lower testosterone levels, according to a new study done at Massachusetts General Hospital in Boston.
Guidelines for administering blood tests for low testosterone, known as “hypogonadism,” recommend two or more tests on different days in the mornings, when testosterone levels are the highest. No guidelines address food intake before testing, but the new study shows that consuming sugar causes blood glucose levels to rise, stimulating insulin production. And the researchers found that insulin can cut testosterone blood levels by as much as 25 percent.
The study examined the result of a standard oral glucose tolerance test on testosterone levels in 74 men. The test revealed that more than 50 percent of the men had normal glucose tolerance, just over 30 percent had prediabetes, and more than 10 percent had Type 2 diabetes. Regardless of whether the men had prediabetes, diabetes, or normal glucose tolerance, the glucose solution lowered testosterone levels by as much as 25 percent.
The testosterone levels stayed lower for at least two hours, and 15 percent of the 66 men who had shown normal testosterone levels before the test showed hypergonadism during the test.
“This research supports the notion that men found to have low testosterone levels should be reevaluated in the fasting state,” Dr. Frances Hayes, the study leader, told Science Daily.
Previous research shows that men with low testosterone levels after the age of 40 may have a higher risk of death than men with normal levels. Levels of testosterone drop gradually with age, declining about 1.5 percent a year after the age of 30.
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