Breast cancer is the most common cancer among women in the world, and its incidence is increasing worldwide. Thyroid disorders are also common among women, particularly hypothyroidism, which is twice as common in women as in men.

Studies have suggested that there may be a link between thyroid disorders, particularly hypothyroidism, and breast cancer. In this article, we will explore the studies that have been conducted on this topic and what their findings have been.

What is the Thyroid?

The thyroid is a butterfly-shaped gland located in the neck that produces hormones that regulate metabolism, heart rate, body temperature, and other bodily functions.

It is regulated by the pituitary gland, which produces thyroid-stimulating hormone (TSH) that signals the thyroid to produce its hormones (T3 and T4).

What is Hypothyroidism?

Hypothyroidism is a condition in which the thyroid gland does not produce enough hormones. This can lead to fatigue, weight gain, cold intolerance, constipation, and other symptoms.

It can be caused by a variety of factors, including autoimmune disorders, radiation therapy, and medications that affect the thyroid gland.

The Studies

Several studies have explored the possible link between hypothyroidism and breast cancer.

One study published in the Journal of Nuclear Medicine found that women with hypothyroidism had a higher risk of developing breast cancer than women without hypothyroidism. The study followed over 30,000 women for 10 years and found that those with hypothyroidism were 2.4 times more likely to develop breast cancer than those without hypothyroidism.

Another study published in the Journal of Clinical Endocrinology and Metabolism found that women with hypothyroidism who were not taking thyroid hormone replacement therapy had an increased risk of developing breast cancer.

The study followed over 10,000 women for 6 years and found that those with untreated hypothyroidism were 1.4 times more likely to develop breast cancer than those without hypothyroidism.

Related Article How Thyroid Function Affects Your Breast Health

A third study published in the journal Thyroid found that women with thyroxine deficiency (a condition in which the thyroid does not produce enough T4) had a higher risk of developing breast cancer than women without thyroxine deficiency.

The study followed over 6,000 women for 8 years and found that those with thyroxine deficiency were 1.9 times more likely to develop breast cancer than those without thyroxine deficiency.

The Possible Mechanisms

The link between hypothyroidism and breast cancer is not well understood, but there are several possible mechanisms that have been proposed.

One theory is that hypothyroidism can lead to an increase in estrogen levels, which can promote the growth of breast cancer cells. Another theory is that hypothyroidism can lead to immune system dysfunction, which can increase the risk of cancer.

In addition, there is evidence to suggest that thyroid hormone receptor beta (TRB) may play a role in breast cancer development. TRB is expressed in breast tissue and has been found to be decreased in breast cancer tissue.

Some studies have suggested that TRB may act as a tumor suppressor, and that deficiencies in TRB may increase the risk of breast cancer.

The Importance of Thyroid Monitoring

Given the possible link between hypothyroidism and breast cancer, it is important for women to have their thyroid function regularly monitored.

Women who have been diagnosed with hypothyroidism should also be vigilant about breast cancer screening and talk to their healthcare provider about any concerns they may have.

Conclusion

While more research is needed to fully understand the link between hypothyroidism and breast cancer, the studies that have been conducted so far suggest that there may be a connection.

Women who have been diagnosed with hypothyroidism should be aware of this possible link and take steps to monitor their thyroid function and breast health.