Is there any association between thyroid autoimmunity and breast cancer?

The relationship between thyroid autoimmunity and breast cancer
is a challenging subject. We aimed to investigate this association in women with
breast cancer.
Methods: In this descriptive study, 41 women with newly diagnosed breast cancer
before receiving any pharmacologic treatment and 38 healthy age-matched
women were enrolled. Anti TPO Ab(anti-thyroid peroxidase antibodies),
FT4(free thyroxine), T3(triiodothyronine) and TSH (thyroid-stimulating
hormone) were measured in both groups.
Results: The mean±SD ages in patients with breast cancer and the control
group were 41.71±1.73 and 40.03±1.74 years, respectively (P=0.496). There
was no statistically significant difference between the mean values of FT4 and
T3 in patients with breast cancer (P=0.447) and the control group (P=0.534).
The mean TSH level in patients with breast cancer was 4.9±1.7 μIU/ml which
was significantly higher than healthy women (1.79±0.15 μIU/ml, P=0.004).
The frequency rate of the increased Anti TPO Ab levels (higher than 35 IU/
ml) in women with breast cancer was 22% which was significantly higher than
the control group (%0, P=0.002), while no statistically significant difference
was found between the mean Anti TPO Ab levels between the two groups
(61.07±29.73 versus 9.78±0.78, P=0.21). Four cases of subclinical and/or overt
hypothyroidism were found in women with breast cancer.
Conclusion: Based on our findings breast cancer patients have higher rates of
thyroid autoimmunity. Measurement of FT4 and T3 in all women with breast
cancer is not recommended but measurement of TSH and Anti TPO Ab levels
seem reasonable.