23rd May 2025

Prolactinoma

Prolactinomas are a type of anterior pituitary adenoma that secrete prolactin (PRL) and lead to hyperprolactinaemia. They are benign tumours of lactotroph cells. Hypersecretion of PRL has inhibitory effects on GNRH and pituitary gonadotrophins. 

They commonly occur in women aged 20-50 years. The ratio of incidence between females and males is 10:1.

Aetiology

• Sporadic
• Multiple endocrine neoplasia syndrome type 1 (MEN-1) 
• Familial isolated pituitary adenoma (FIPA)

Tumour Classification

This is based on tumour size

• Microadenoma
  • <10mm diameter
  • Commonest
  • Unlikely to get larger
• Macroadenoma
  • >10mm diameter
  • Often locally invasive to suprasellar/parasellar areas
  • Can compress vital structures
  • Often benign and do not metastasise to outside the pituitary sella

Clinical Presentation

• Premenopausal women: Hypogonadotropic hypogonadism- infertility, oligo/amenorrhea, galactorrhoea, reduced bone density
• Men: Hypogonadotropic hypogonadism- reduced energy, decreased libido, lowered muscle mass, reduction in body hair, galactorrhoea, decreased bone density
• Postmenopausal women: Tumour often detected as an incidental finding on brain imaging. Or, mass effects from tumour produce symptoms, e.g., unilateral/bi-temporal hemianopia, which prompt investigation

Investigations

• Random serum prolactin level. The concentration often reflects the size of the tumour
  • Any PRL level above the normal age range suggests prolactinoma
  • PRL > 250 micrograms/L: prolactinoma likely
  • PRL > 500 micrograms/L: macroadenoma likely
  • Note: medications such as risperidone and metoclopramide can increase PRL levels
• Pituitary MRI
• Formal visual field testing for macroadenomas
• Consider genetic screening in patients <30 years with macroadenomas for
  • MEN-1
  • Aryl hydrocarbon receptor-interacting protein (AIP) gene mutations present in FIPA
• Consider other tests for hypopituitarism such as IGF-1, ACTH, TSH
• U&Es to assess kidney function as CKD can lead to a decrease in PRL clearance

Management

• Pre-menopausal women with asymptomatic microadenomas: observation
• Pre-menopausal women with symptomatic microadenomas that do not wish to be pregnant:
  • 1st: Dopamine agonist e.g., Cabergoline
  • 2nd: Combined oral contraceptive pill, especially if only symptom menstrual changes
  • 3rd: transsphenoidal surgery
  • 4th: sellar radiotherapy
• Pre-menopausal women with symptomatic microadenomas that do wish to be pregnant OR microadenomas in men OR macroadenomas in any patient:
  • 1st: dopamine agonist
  • 2nd: transsphenoidal surgery
  • 3rd: sellar radiotherapy
• Microadenomas in post-menopausal women: observation

Monitoring and follow-up

• Pituitary MRI every year initially 
• Regular perimetry
• Regular measurements of PRL levels
• ECHO monitoring for patients on high dose cabergoline due to side effect of valve pathology

Complications

• Bi-temporal hemianopia
• Hypopituitarism 
• Cabergoline associated valvular pathology
• Pituitary apoplexy