The most characteristic symptom of hyperprolactinaemia is galactorrhoea. This is a milky discharge, usually bilateral, found in women and sometimes men. Galactorrhoea is the most common presenting complaint of hyperprolactinaemia, but it is important to realise that hyperprolactinaemia can be present without galactorrhoea.
Other characteristic symptoms of hyperprolactinaemia are infertility, amennorhoea (absent periods), and loss of libido. These symptoms are as a result of the ability of prolactin to negatively feedback on LH release from the hypothalamus and also to decrease the gonadal response to gonadotrophins.
In men, the most common features of hyperprolactinaemia are loss of libido and impotence.
When the cause of the hyperprolactinaemia is from an adenoma, there may be other symptoms as a result of local pressure and invasion from the tumour. The most common of these defects is when there is a suprasellar extension that compresses the optic nerve and results in visual field defects. The most common of these visual field defects is when the patient complains of 'tunnel vision' (bitemporal hemianopia). Some of the larger tumours can compress the other tissue in the pituitary and cause varying degrees of hypopituitarism.