We have investigated the controversial association between diseases of
the thyroid gland and breast carcinoma using methodology which allows
positive exclusion of cases of breast disease from control groups and
the defection of subclinical alterations in thyroid volume using high
resolution ultrasonography, thus addressing the deficiencies of earli
er studies, Whereas the prevalence of hyperthyroidism and hypothyroidi
sm in patients with breast carcinoma and in healthy controls without c
linical evidence of breast disease was similar, non-toxic goitre was m
ore than twice as common in the breast carcinoma patients, Thyroid vol
umes were also significantly higher in breast carcinoma patients than
in control; using World Health Organisation criteria, 45.5% of breast
carcinoma patients had thyroid enlargement compared with only 10.5% of
controls, Finally, antithyroid peroxidase autoantibodies were twice a
s common in breast cancer patients than in controls, These findings pr
ovide clear evidence of a relationship between thyroid disease and bre
ast carcinoma, although the mechanisms underlying this relationship re
quire further study, future studies of breast cancer risk factors shou
ld therefore include assessment of thyroid function, antibody status a
nd volume.