24th May 2025

Galactorrhoea

Galactorrhoea is characterised by milky nipple discharge unrelated to pregnancy or breastfeeding and can be physiological or pathological in nature. It can affect as many as 1 in 4 women and can occur at any age, including after menopause. Raised serum prolactin levels are responsible for the discharge, of which there are many underlying causes.

Physiological nipple discharge can be attributed to several factors, one of which is excessive nipple stimulation. This can be through sexual activity, frequent breast examinations (including imaging) or high-impact exercise. Stress is also known to increase serum prolactin levels, which can result in galactorrhoea.

Pathological nipple discharge can be secondary to a wide variety of endocrine and iatrogenic factors. Hyperprolactinaemia can be associated with disorders of the hypothalamic-pituitary axis, of which lactotroph adenomas are the most common. Accounting for up to 40% of all pituitary adenomas, lactotroph adenomas are usually benign sporadic prolactin secreting tumours, though occasionally they may form part of an underlying Multiple Endocrine Neoplasia Type 1 (MEN 1) Syndrome. Disorders affecting the hypothalamus may also lead to increased prolactin levels, usually by way of reduced dopaminergic inhibition of the pituitary gland. These can include benign tumours (such as craniopharyngioma), malignancy (such as metastatic breast carcinoma), infiltrates (such as sarcoidosis) or trauma.

Drug induced hyperprolactinaemia is also a common cause of pathological galactorrhoea. The most common cause of pharmacologically induced hyperprolactinaemia is antipsychotic medication, typically due to their antagonistic effect on dopamine receptors. Other medications that have been associated with raised prolactin levels include selective serotonin reuptake inhibitors (SSRIs), the gastric motility drugs Metoclopramide and Domperidone, Methyldopa and Verapamil.

Other less common causes of galactorrhoea include familial hyperprolactinaemia (characterised by a germline, loss of function mutation in the prolactin receptor gene PRLR), hypothyroidism, macroprolactinaemia (aggregates of prolactin and antibodies) and chronic kidney disease.

Investigations and treatments for galactorrhoea are dependent upon the underlying cause. Evaluation usually requires an extensive history, coupled with clinical examination, serum prolactin levels and imaging, such as an MRI scan of the pituitary gland. The presence of galactorrhoea alone does not always necessitate treatment, unless it is bothersome to the patient. When indicated, the pharmacological treatment for lactotroph adenomas and idiopathic hyperprolactinaemia usually involves the introduction of a dopamine agonist, such as Cabergoline or Bromocriptine. Larger tumours that are unresponsive to initial medical therapy may require more invasive measures, such as transsphenoidal surgery and postoperative radiotherapy. Drug induced hyperprolactinaemia can be managed through patient counselling and education surrounding medication side effects. In some circumstances, dose tapering or discontinuing the medication may be required.