Thyroid-stimulating hormone and prolactin levels in breast cancer.

Serum thyroid-stimulating hormone (TSH) and prolactin (PRL) levels were measured before and after intravenous administration of protirelin to 148 patients with breast carcinoma. There was a high prevalence (36%) of elevated basal TSH; however, most of the patients were euthyroid and had normal serum thyroxine and T3 resin uptake. The PRL level was elevated in 22% of the cases. Both the mean PRL and the mean TSH levels for the breast cancer patients were significantly elevated above the respective means in a control group. We could find no correlation between serum TSH and PRL levels, suggesting that the purported association between a decreased thyroid state and breast cancer is probably not mediated through an increased PRL level. The mean survival and mean disease-free interval were shorter for patients with either elevated TSH or elevated PRL levels, but in neither case was the difference statistically significant.