Galactorrhoea refers to breast milk production not associated with pregnancy or breastfeeding. Breast milk is produced in response to the hormone prolactin.
Prolactin is produced in the anterior pituitary gland. It is also produced in other organs, such as the breast and prostate. Prolactin also regulates aspects of immune function and metabolism.
Dopamine blocks the secretion of prolactin. Therefore, dopamine antagonists (i.e., antipsychotic medications) can result in raised prolactin and galactorrhea. Dopamine agonists (e.g., bromocriptine or cabergoline) can be used to suppress prolactin secretion.
Pregnancy and Breastfeeding
Milk production may start in small amounts during the second or third trimester of pregnancy, and leaking can occur during that time. Oestrogen and progesterone inhibit the secretion of prolactin. In pregnancy, higher levels of oestrogen and progesterone inhibit breast milk production.
Oxytocin stimulates breast milk excretion. Full milk production starts shortly after birth in response to oxytocin release and a rapid drop in oestrogen and progesterone.
Breast milk production will taper off and stop once breastfeeding stops.
Hyperprolactinaemia
Galactorrhoea is usually associated with a raised prolactin level (hyperprolactinaemia).
There is a long list of causes of hyperprolactinaemia, but the key causes to remember are:
- Idiopathic (no cause can be found)
- Prolactinomas (hormone-secreting pituitary tumours)
- Endocrine disorders, particularly hypothyroidism and polycystic ovarian syndrome
- Medications, particularly dopamine antagonists (i.e., antipsychotic medications)
Prolactin suppresses gonadotropin-releasing hormone (GnRH) by the hypothalamus, leading to reduced LH and FSH release. Therefore, hyperprolactinaemia can also present with:
- Menstrual irregularities, particularly amenorrhoea (absent periods)
- Reduced libido (low sex drive)
- Erectile dysfunction (in men)
- Gynaecomastia (in men)
Prolactinomas
Prolactinomas are tumours of the pituitary gland that secrete excessive prolactin. This may be associated with multiple endocrine neoplasia (MEN) type 1, an autosomal dominant genetic condition.
Prolactinomas can be:
- Microprolactinomas – smaller than 10 mm
- Macroprolactinomas – larger than 10 mm
Macroadenomas can have adverse effects relating to their size:
- Headaches
- Bitemporal hemianopia (loss of the outer visual fields in both eyes)
The optic chiasm sits just above the pituitary gland. The optic chiasm is the point where the optic nerves coming from the eyes cross over to different sides of the head. Only the nerves fibres containing the signal from the outer visual fields cross over, whereas the fibres from the inner visual fields continue on the same side. A pituitary tumour of sufficient size will start to press on the optic chiasm, where the nerves cross, leading to a visual field defect, with loss of vision in the outer visual fields in both eyes (the inner visual fields are spared). This is called bitemporal hemianopia.
TOM TIP: It is worth properly understanding and remembering bitemporal hemianopia, as it is commonly tested in exams. If you find it a bit confusing, there is a Zero to Finals YouTube video explaining it in detail. Remember to examine the visual fields in any patient with symptoms that may be related to a pituitary tumour.
Non-Milk Discharge
Other conditions can cause nipple discharge that is not breast milk:
- Mammary duct ectasia
- Duct papilloma
- Pus from a breast abscess
Investigations
A pregnancy test is essential in women with childbearing potential presenting with breast milk production.
Blood tests include:
- Serum prolactin
- Renal profile (U&Es)
- Liver function tests (LFTs)
- Thyroid function tests (TFTs)
An MRI scan is the investigation of choice for diagnosing pituitary tumours.
Management
Management is targeted at the underlying cause.
Dopamine agonists (e.g., bromocriptine or cabergoline) can be used to treat the symptoms of hyperprolactinaemia. They block prolactin secretion and improve symptoms.
Trans-sphenoidal surgical removal of the pituitary tumour is the definitive treatment of hyperprolactinaemia secondary to a prolactinoma. The pituitary gland and tumour are accessed and removed through the nose and sphenoid bone.
Last updated June 2021
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