Tuberoinfundibular dopamine (prolactin-inhibiting factor)
Hypothalamus · Dopamine D2 Tonic inhibition
Arcuate dopaminergic neurones send dopamine down the portal veins onto lactotroph D2 receptors. Prolactin is the only anterior pituitary hormone under tonic inhibition, so anything that interrupts that supply raises it.
Detail
- Consequence
- Cut the stalk and every anterior pituitary hormone falls except prolactin, which rises
- Short loop
- Prolactin stimulates its own tuberoinfundibular dopamine neurones
- Raise prolactin
- Antipsychotics (risperidone, haloperidol, amisulpride), metoclopramide, domperidone, methyldopa, oestrogen, opioids
- Lower prolactin
- Cabergoline and bromocriptine (D2 agonists), which shrink prolactinomas as well as lowering the level
When it goes wrong
Risperidone or metoclopramide
Hyperprolactinaemia with galactorrhoea, amenorrhoea or erectile dysfunction, typically 1000-3000 mIU/L (50-150 microgram/L) and reversible on stopping
Antipsychotic that cannot be stopped
Switch to aripiprazole, a partial D2 agonist, which lowers prolactin
Practise this structure
2 questions in the bank tagged Pituitary.
A 52-year-old woman has progressive headaches and difficulty seeing objects to either side. MRI shows a 2.6-cm sellar mass elevating and compressing the optic c…
Clinical rotations · middle twist
A 44-year-old man has an incidental 8-mm pituitary lesion discovered during MRI for headaches. He has normal visual fields, normal pituitary hormone testing, an…
Clinical rotations · middle twist