The two principal causes are:
- mechanical stimulation of the breasts
The latter is due to neuroendocrine reflex secretion of prolactin and is the most likely explanation in a woman with a normal menstrual cycle who has recently finished breast feeding. The woman may check her breasts for milk out of curiosity. Alternatively, physical stimulation may occur during intercourse.
Less commonly, galactorrhoea may occur whilst taking antidepressants (especially selective serotonin reuptake inhibitors), combined oral contraceptives, major tranquilisers and related preparations e.g. anti-emetics such as prochlorperazine, or methyldopa.
Last reviewed 01/2018