Hyperprolactinaemia is an excess of prolactin levels in blood serum, which can be associated with menstrual cycle abnormalities that can progress sequentially as the level of prolactin increases: from an inadequate luteal phase with almost regular cycles to intermittent anovulation with oligomenorrhoea to total anovulation and amenorrhoea. The gene discussed is PRL; the disease is hyperpituitarism.