Thirdly, it could be due to a benign tumour which is itself producing prolactin. This sort of tumour is called a prolactinoma. Prolactinomas are usually less than half an inch across although they can occasionally be larger. They tend to interfere with production of sex hormones. Women are likely to have the small prolactinomas and symptoms are likely to be problems with fertility or periods, and possibly also production of breast milk when not pregnant or breastfeeding.
Men often have the larger prolactinomas and symptoms include loss of sex drive, and impotence.
In both sexes, treatment with tablets is usually very effective, restoring sex drive and fertility, often very quickly. For further details, please see our leaflet on ' Prolactinoma '. You may find that your field of vision gets smaller - rather as if you were wearing blinkers. This can happen to one eye or to both, and may be accompanied by a headache. You may be seen by an eye specialist as well as by your endocrinologist if you have visual problems.