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PRESS RELEASE
UNDER EMBARGO UNTIL 00.01 GMT THURSDAY 11 FEBRUARY
2016
Breast cancer risk higher in women with
overactive thyroid
High levels of thyroid hormone are associated with an increased risk of breast cancer in
women, according to a 36 yearlong study of more than four million women published today
in the European Journal of Endocrinology.
The thyroid is an important gland that releases hormones which control our metabolism; up
to 6.7% of Europe’s population have undiagnosed thyroid disease. Hyperthyroidism, in which
the gland makes too much thyroid hormone, occurs in 51 per 100 000 people per year, and
is six times more common in women than in men.
In this study, researchers from Aarhus University Hospital followed 4,177,429 women living
in Denmark between 1978 and 2013, accounting for all the women registered and using
Denmark’s health service over the entire 36 year period. Only women with a first-time
diagnosis of thyroid disease and no history of cancer were included.
They found that 80,343 women were diagnosed with hyperthyroidism (too much thyroid
hormone) and 61,873 with hypothyroidism (too little thyroid hormone). Hyperthyroid women
were 11% more likely to develop breast cancer, whereas those with hypothyroidism were 6%
less likely to develop the condition, compared to women in the general population.
“In vitro experiments show that sex hormones such as oestrogen play an important role in
the proliferation of breast cancer cells”, said lead author of the study Dr Mette Søgaard.
“High levels of thyroid hormone levels can have oestrogen-like effects, which may explain
why hyperthyroidism is associated with higher risk of breast cancer.”
The research team’s next step is to investigate whether using thyroid hormones to treat
hypothyroidism may also be associated with an increased breast cancer risk.
“Our findings emphasize the importance of raising awareness of breast cancer in women
with hyperthyroidism, and further our understanding of this potential risk,” said Dr Søgaard.
--------ENDS------Notes for editors:
1. For further information about the study please contact the authors.
Professor Jens Otto Lunde Jørgensen
Clinical Professor, Endocrinology and Internal Medicine
Aarhus University Hospital
Tel: 0045 207 27383
Mob: 0045 78462025
Email: [email protected]
2. The study Hypothyroidism and hyperthyroidism and breast cancer risk: a nationwide cohort
study will be published in the European Journal of Endocrinology the day the embargo lifts.
For copies of the study, please contact the press office using the details below.
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