Post-meal surges in blood sugar can cut a man's level of circulating testosterone by about a quarter, a new study has revealed.
According to study's researchers, the finding might help doctors decide to test for testosterone levels while patients are fasting.
The study involved 74 men, including 42 with normal blood sugar, 23 with impaired blood sugar levels ("pre-diabetes") and nine newly diagnosed with type 2 diabetes.
Each of the men drank a sugary solution (75 grams of pure glucose), which typically triggers a spike in blood sugar levels. They then had their testosterone levels tested.
The researchers found that, regardless of whether the men had diabetes or not, blood levels of testosterone dropped by as much as 25 percent after they drank the sugary drink.
This trend continued for more than two hours after the glucose was ingested. In fact, 15 percent of the 66 men with normal testosterone levels before the test had low testosterone ("hypogonadism") at some point during the test.
The researchers said that changes in insulin levels didn't seem to affect the results, nor did levels of other hormones.
Study co-author Dr. Frances Hayes, an endocrinologist at St. Vincent's University Hospital in Dublin, Ireland, said that doctors need accurate testosterone testing to see whether men are hypogonadal and require testosterone supplementation.
Hayes, who did the research at Massachusetts General Hospital, Boston, said that because testosterone now seems tied to blood-sugar levels, "this research supports the notion that men found to have low testosterone levels should be re-evaluated in the fasting state."
The results were presented at The Endocrine Society's 91st Annual Meeting in Washington, D.C.