Hyperprolactinaemia and the regular menstrual cycle in asymptomatic women: should it be treated during therapy for infertility?

It is known that hyperprolactinaemia can cause galactorrhoea and irregular cycles or even amenorrhoea. High serum prolactin (PRL) can disturb follicular maturation and corpus luteum function. Treatment of hyperprolactinaemia in patients with resulting bleeding anomalies is established, but the question is how to manage normal cyclic hyperprolactinaemic women? Studies have shown that in a subgroup of asymptomatic patients the serum contains mainly high molecular weight form (big big PRL), which has a low bioactivity, called macroprolactinaemia. It is evident that macroprolactin does not affect the control of pituitary PRL secretion via the short loop feedback mechanism or the secretion of gonadotrophins as does monomeric PRL. Identification of macroprolactinaemia is therefore clinically important to prevent unnecessary examinations and inappropriate treatment. Prolactinoma can be associated with macroprolactinaemia. Performance of pituitary imaging in asymptomatic patients with hyperprolactinaemia may therefore be justified, but further studies are needed to evaluate the relation of costs and benefit. An unsolved problem is the differentiation between inactive and PRL-secreting tumours. Caution should be exercised concerning medical treatment in unstimulated patients and also in patients during ovarian stimulation alone or in combination with intrauterine insemination or in-vitro fertilization. The potential clinical significance of hyperprolactinaemia/macroprolactinaemia in asymptomatic women must be further evaluated.