High levels of insulin may play a stronger role in the development of breast cancer than was previously thought, a new study suggests.

Researchers at Albert Einstein College of Medicine of Yeshiva University say that by targeting insulin levels in the blood, they may be able to develop new health resources that fight cancer.

Previously, scientists had uncovered a connection between obesity and postmenopausal breast cancer, but they assumed estrogen was responsible for the link.

In the new study, researchers looked at other hormonal imbalances, such as insulin, while controlling for estrogen levels.

They found that participants who had the highest insulin levels were up to 50 percent more likely to develop breast cancer than those with the lowest levels. Furthermore, the link between obesity and cancer weakened when insulin was involved.

“This means that a large component of that obesity-cancer relationship may be mediated by insulin levels,” said Professor Marc Gunter. “Among these women, the influence of insulin on breast cancer risk was quite high.”

Previous research has suggested that low melatonin levels may also influence the development of breast cancer among postmenopausal women.