Abnormalities in evening plasma prolactin levels in nulliparous women with benign or malignant breast disease.

In the present study the assay results of prolactin concentrations in serial samples of blood obtained from premenopausal women with benign or malignant disease of the breast are compared with--and discussed in relation to--findings reported in earlier studies based on single samples of blood taken at various times from a large and ostensibly normal population of women. The finding of an abnormality in nycthemeral prolactin levels in the established disease is considered to strengthen the concept that the same abnormality found in high-risk groups is of aetiological importance.