Increased plasma prolactin levels in a group of men with breast cancer--a preliminary study.

Gonadal and hypophyseal hormones were investigated in 15 males with breast cancer and 15 tumour referents, on average 1 month postoperatively. Plasma prolactin was found to be significantly more often elevated in men with breast cancer compared with referents (p less than 0.005). Another group of men with breast cancer disclosed a tendency for lower S-FSH levels compared with the referents (p less than 0.01). No significant difference was seen between cases and referents regarding S-LH, p-estradiol or p-testosterone. The size of the primary breast tumour was correlated with a higher prolactin level. The findings lend support to a theory implicating prolactin and possibly prolactinomas as a risk factor for the disease in males.