Hyperprolactinaemia, reflecting sustained overproduction from the pituitary, is relatively common in the population. The causes are listed in Box 1. The commonest cause is the use of drugs that have dopamine D2 receptor antagonist activity, including antipsychotic agents such as phenothiazines, although some newer agents have little effect. Pregnancy and lactation are the commonest physiological causes, and short- term acute stress, such as the anxiety provoked by blood sampling, is also a frequent cause of transient rises in serum prolactin that may be misinterpreted in clinical practice and necessitate a second confirmatory blood sample.
Box1. Causes of hyperprolactinaemia
Pathological pituitary causes of hyperprolactinaemia may reflect a functioning pituitary prolactinoma, a prolactin- secreting microadenoma or macroadenoma, but in many cases no adenoma is detectable on scanning, in which case the condition is termed idiopathic or non- tumoural hyperprolactinaemia. Anatomical disturbance in the suprasellar region may cause effective functional dis connection of the anterior pituitary gland from the inhibitory effects of dopamine: the resulting ‘stalk disconnection’ hyperprolactinaemia may lead to diagnostic confusion between functioning prolactinomas and non- functioning pituitary adenomas or other non- pituitary lesions, which usually require different management.
Prolactin hypersecretion can coexist with various conditions. Prolactin is frequently cosecreted with growth hormone by mammo somatotroph cells, and mixed GH- prolactin- secreting tumours can present clinically as either acromegaly or hyperprolactinaemia. Thus the evaluation of hyperprolactinaemic patients should con sider the possibility of acromegaly. Hyperprolactinaemia com plicates the presentation of polycystic ovarian syndrome in up to 30% of patients [14], though the mechanism and nature of the as sociation remain uncertain. Other miscellaneous recognized causes of hyperprolactinaemia include hypothyroidism, nipple, or chest wall stimulation (including herpes zoster, burns, nipple piercings), chronic renal failure, and cirrhosis.
