A just published study has found that women with an overactive thyroid known as hyperthyroidism, have an increased risk of 11% for developing breast cancer in comparison to women who have thyroid glands that are functioning properly.
In contrast, the opposite condition hypothyroidism where the gland produces low levels of hormones. Women with hypothyroidism have a 6% reduction in a risk for breast cancer compared to women with thyroids glands that are functioning normally.
A team of researchers from Denmark analyzed data for nearly 80,000 women who had hyperthyroidism and more than 61,000 women who had hypothyroidism.
At the beginning of the study, each of the Danish women were free of cancer and were followed 36 years between 1978 and 2013.
The team of researchers monitored the occurrence of breast cancer for the women each five to seven years.
The findings said researchers were not that surprising even though the patients had been tracked for longer than other studies searching for the same.
Researchers added that the link between breast cancer and hyperthyroidism was documented in other prior studies. They also mentioned that even though there exists an association, it does not necessarily mean hyperthyroidism causes breast cancer.
The doctors said that women with a thyroid disease are much more apt to see the doctor and to undergo exams including a mammography.
The lead author for this research said that the thyroid hormones could play some part in the development of breast cancer and that the treatment for hyperthyroidism could also increase the risk.
The researchers said that high thyroid gland hormone levels could have effects that are estrogen like which might explain why the hyperthyroidism is linked with a higher risk of developing breast cancer.
The researchers also said that women are more apt to have hyperthyroidism as for every 100,0000 people, 51 become diagnosed with the condition.