Prolactinaemia

Prolactinaemia

·        Physiology:

o   PRL has pulsitile and diurnal pattern: rises dramatically during sleep

o   Dopamine inhibits prolactin

o   PRL is raised by: 

§  Oestrogen ® slightly ­PRL (ie women higher than men)

§  TRH ® slightly ­PRL (used in pituitary stimulation test)

§  T5 Dermatome stimulation ® ­PRL (but breastfeeding won‟t increase the size of a prolactinoma)

§  PRL rises through pregnancy 

§  Drugs: most major tranquillisers (ie antipsychotics), Metoclopramide (Maxolon) therapy for nausea blocks dopamine ®­PRL. Aldomet (alpha-methylDOPA) is the only hypotensive agent which increases prolactin (via dopamine depletion)

§  Can rise due to emotional or physical stress (including stressful venipuncture ® artefact)

§  High in chronic renal failure

§  Hypothyroidism ® ­TRH ® ­PRL

§  Sarcoidosis

§  Post-pill amenorrhoea (if due to other causes usually resolves < 1 year)

o   PRL level is not effected by Progesterone or nausea

·        Most common pituitary presentation.  Presents early in women (amenorrhoea), late in men

·        Symptoms:

o   Women: ¯libido, weight gain, apathy, vaginal dryness (due to hypooestrogen), amenorrhoea (very sensitive to ­PRL, infertility due to ­PRL ® ¯LH peak, ­PRL suppresses progesterone), galactorrhoea (will need to differentiate from breast inflammatory exudate – clear or green). If infertility, always check the man (cause of 1/3 of problems of infertility)

o   Men: impotence, ¯libido, reduced facial hair, local pressure effects, galactorrhoea (30%), mildly ¯testosterone (but asymptomatic). Not gynaecomastia (usually only in ¯testosterone or ­oestrogen)

·        Investigations: basal prolactin between 10.00 – 12.00 h (repeat 2 – 3 times), CT, MRI, assess pituitary function

·        Management:

o   If tumour < 10 mm (unlikely to be seen on Xray): bromocriptine to restore fertility avoids complications of ¯oestrogen due to ­PRL (could take pill instead). May ® postural hypotension. Commence slowly otherwise nausea. Good prognosis. No known teratogenic effects of bromocriptine – but still withdrawn on becoming pregnant if possible

o  Treat macroadenoma with surgery if bromocriptine fails to reduce size of PRL. But if pressure effects or pregnancy is contemplated then surgery. Monitor PRL

·        Prolactin deficiency causes failure of lactation but has no other know ill effects.  Deficiency is very rare