An abnormal luteal-phase evening peak of plasma prolactin in women with a family history of breast cancer.

In earlier study an abnormally high lutealphase evening peak of plasma prolactin in women with a family history of breast cancer was first noted, but there were few observations. The current study confirms the original findings. Other groups, e.g. nulliparous women and tall and heavy women also appear to show the same abnormality. Further work is required to establish this finding. However, the abnormally high luteal-phase evening peak of plasma prolactin in the family history group is still present when such women are disregarded. The possible relevance of the restriction of elevated prolactin levels, in enhanced-risk women, to the luteal phase, when both oestradiol and progresterone levels are also elevated, is discussed briefly as is the question why a minor peak at 19.00 h is important when plasma prolactin levels show a massive increase between 03.00 and 09.00 h.