[The thyroid gland and the breast]

The results of experimental clinical and epidemiological studies published so far from 1896 until today on the connection between thyroid and breast diseases doubtless require critical examination, since these results are highly contradictory. Without being able to go into details of the sources of methodological errors and the highly heterogenous investigation material, two pathophysiological mechanisms can be discussed in the investigation of the interrelationship between the thyroid and the breast: 1. A low level of thyroid hormone might make the breast hypersensitive to prolactin, which might induce dysplasia or neoplasia of the mammary epithelium. In addition, there is the almost identical neurohumoral regulation of the hormones of the thyrotropic and lactotropic cells in the anterior pituitary. 2. Thyroid hormones have an effect on peripheral androgenic and estrogenic metabolism. The hyperthyroid state may cause an increase in the concentration of sex hormone-binding globulins, which might give rise to an alteration of the beneficial effect of sex hormones on the cellular levels. Compared to this, the iodine deficit might lead to neoplastic transformation of the mammary epithelium via the enhanced gonadotropin stimulation and the subsequent chronic hyperestrogenism. For better understanding of the always topical problem of the not yet completely elucidated correlation between thyroid function and breast diseases, a two-track procedure is appropriate: 1. Thyroid receptor assay on animal and human breast tumor tissue and 2. prospective clinical studies on a large scale.(ABSTRACT TRUNCATED AT 250 WORDS)