Why does hyperprolactinaemia cause irregular periods?

Prolactin is a hormone made by the pituitary gland. When its level stays high outside the expected pregnancy or breastfeeding setting, it can reduce the brain signals that stimulate the ovaries. Ovarian hormone release may then become less predictable, ovulation may happen late or not at all, and bleeding may arrive at changing intervals.

Possible contributors include medicines, thyroid problems, pituitary conditions, pregnancy, breastfeeding, and other health changes. A blood test is interpreted alongside symptoms, timing, medicines, and sometimes repeat testing because prolactin can vary with stress and other factors.

Keep a record of bleeding dates, flow, nipple discharge, headaches, vision changes, and medicines or supplements. Arrange an appointment if cycle changes persist or affect fertility. A clinician may check pregnancy status, prolactin, thyroid function, and other hormones, then decide whether further assessment is needed.

Seek prompt care for a severe or new headache, vision changes, fainting, very heavy bleeding, or severe pelvic pain. These symptoms can have causes other than prolactin changes and should be assessed without delay.

Ask whether a medicine or thyroid problem could be raising prolactin, whether the test should be repeated, how results affect fertility planning, and what symptoms would require imaging or specialist review.