Thyroid function in women with fibrocystic changes of the breast

Thyroid hormones are directly acting on the breast gland through its receptors and also indirectly. Indirect action takes place mainly by hypothalamus-pituitary-ovarian axis, as well as, by influencing prolactin (PRL) secretion. There is a functional relationship between thyrotropin-stimulating hormone (TSH) secretion and the concentration of PRL in the blood.

Both hypothyroidism and hyperthyroidism predispose to fibrocystic changes in the breast, however the majority of women with those changes are found to be in the euthyreosis status.
Presently a view dominates that a decreased level of sex hormone binding globuline (SHBG) accompanying hyperthyroidism results in higher concentration of free estradiol. An increase of conversion of androstenedione to estrone is found in thyrotoxicosis.

The above-mentioned mechanism leads to hyperestrogenism, whose influence on the breast gland is negative.

It was stated on the basis of experimental studies in animals, as well as, clinical ones in women that hypothyroidism and also hyperthyroidism were frequently leading to fibro-cystic changes in their breasts.

A view prevails that women with low concentration of free thyroxine, mild hypothyroidism, delayed menopause constitute a higher risk group of breast cancer incidence.
The authors of this study on the basis of reference review, suggest the need of drawing particular attention to the clinical and biophysical condition of the breast gland in women with thyroid function disturbances.