Elevated risk for diabetes and weight gain is a well-documented issue for post-menopausal women—but its biological cause isn’t as certain.

Contradicting past studies, researchers at the Wisconsin National Primate Research Center (WiNPRC) have learned that a naturally-occurring decline in one specific hormone may not be a significant factor in post-menopausal health risks, as previously thought. An article published July 19 in the International Journal of Obesity shows a much smaller role for ovarian estradiol—a steroid hormone—in female metabolism than previously thought.

In prior studies with adult female rodents, ovarian estradiol has been shown to regulate body weight, energy balance and other factors while also protecting against diet-induced obesity.

“We thought these actions also occurred in primates, but our research indicates otherwise,” said Marissa Kraynak, PhD, who co-authored the study with Ricki Colman, PhD.

To test the metabolic functions of ovarian estradiol in female nonhuman primates and discover what happens when the hormone is removed, scientists at WiNPRC selected the common marmoset monkey, which is modestly susceptible to diet-induced obesity. They studied the effects of estradiol depletion combined with diets higher in fat and sucrose, hypothesizing that this would increase body weight and decrease glucose tolerance.

“But we were surprised to see no changes in feeding behavior, activity or energy expenditure in our study monkeys,” Kraynak noted.

The study results suggest that ovarian estradiol may not be a major contributor to metabolic health in female primates. This also leaves open the intriguing possibility that estrogens produced elsewhere in the body—including the brain—may function in this capacity in both nonhuman primates and women.