Hypothalamic-pituitary-thyroid axis in breast cancer

The plasma concentration of thyroid-stimulating hormone (T.S.H.) was measured by radioimmunoassay before and 20 and 60 minutes after the intravenous injection of 200 μg. of thyrotrophin-releasing hormone (T.R.H.) in fifty women with early and fifty women with advanced cancer of the breast. Results were compared with those obtained in a group of fifty age-matched women who were in hospital awaiting surgery for a variety of conditions. The mean basal level of T.S.H. in both the breast-cancer groups was significantly higher than in the controls; more cancer patients had T.S.H. levels above the normal range, while fewer had levels below the sensitivity of the assay. After T.R.H. stimulation, a significantly higher mean T.S.H. response was obtained in the breast-cancer groups both at 20 minutes and at 60 minutes; approximately three times as many cancer patients as controls had an exaggerated response, and fewer had an impaired or absent response to T.R.H. It is suggested that breast-cancer patients as a group have a level of thyroid function which is lower than that found in women in hospital with conditions unrelated to the breast, and that this lowered function is of primary thyroid and not of pituitary or hypothalamic origin