Raised prolactin

A patient is hyperprolactinaemic if the serum concentration of prolactin is elevated.

Hyperprolactinaemia may be

• physiological, due to:
  • pregnancy
  • lactation
  • stress
    
    
• pathological, due to for example:
  • drugs
  • a prolactinoma or other cerebral tumour
  • ectopic prolactin synthesis

What level of prolactin is significant?(1)

• mildly increased prolactin levels (400-600mu/L) may be physiological and asymptomatic but higher levels are usually pathological
  • should be repeated to confirm hyperprolactinaemia
• very elevated levels (above 5,000mu/L) usually imply a prolactin-secreting pituitary tumour

Note that reference ranges vary between laboratories.

Notes:

• prolactin secretion varies with time, resulting in serum levels being 2-3 times higher at night than during the day. The levels of prolactin in normal individuals also tend to rise in response to physiological stimuli, including sleep, exercise, pregnancy and surgical stress (2)
• most patients with a prolactinoma are women
• reliance on a single, non-rested prolactin value may lead to over-diagnosis of hyperprolactinaemia. A resting sample should be considered with random values <2,000 mU/L (94 ng/mL) (3)

Reference:

• GPonline. Hyperprolactinaemia: diagnosis and management (Accessed July 28th 2018)
• South Tees Hospitals NHS Foundation Trust. Prolactin. (Accessed July 28th 2018)
• Whyte MB et al. Importance of cannulated prolactin test in the definition of hyperprolactinaemia. Pituitary. 2015 Jun;18(3):319-25