Hyperprolactinaemia and prolactinoma

Definition

Prolactinoma

• Definition of the size limit: microprolactinoma < 10 mm, macroprolactinoma ≥ 10 mm.
• What is additionally checked for a macroadenoma: visual field (chiasm proximity).

• Hyperprolactinaemia is a raised serum prolactin concentration; a prolactinoma is a benign pituitary adenoma composed of lactotroph cells and the most common hormone-secreting pituitary tumour.

Classification

• By size, microprolactinomas below 10 mm, macroprolactinomas above 10 mm and giant prolactinomas above 4 cm are distinguished.

Occurrence & epidemiology

Epidemiology

• Prolactinomas account for about 40% of all pituitary tumours; between the ages of 20 and 50, women are affected about ten times more often than men, and microadenomas predominate in women.

Aetiopathogenesis

Aetiology and pathogenesis

• Physiological causes include pregnancy, the postpartum period, nipple stimulation, stress, sleep and sexual intercourse.
• Pharmacological causes include dopamine receptor blockers such as risperidone, haloperidol and metoclopramide, antidepressants such as tricyclics and fluoxetine, as well as opioids and oestrogens.
• Besides prolactinoma, pathological causes include lesions of the hypothalamus and pituitary stalk, such as a stalk effect from non-functioning tumours, chronic renal failure, liver cirrhosis and primary hypothyroidism via raised TRH.

Clinical features

Clinical Presentation and Initial Steps

• Typical symptoms: galactorrhoea, cycle disorders/amenorrhoea, infertility.
• Why the cycle is disturbed: suppression of pulsatile GnRH secretion.
• Most common cause in practice: drugs (neuroleptics, MCP, antidepressants).
• Therefore, first: medication history.
• Other causes: hypothyroidism, renal insufficiency, stress.
• Before imaging, one determines: TSH, free thyroid levels, control value.

• In women, galactorrhoea, oligo- or amenorrhoea and infertility predominate; oestrogen deficiency may cause dyspareunia, reduced libido and low bone density up to osteoporosis.
• Space-occupying macroadenomas cause headache, visual field defects, cranial nerve deficits and hypopituitarism; these mass effects predominate mainly in men.

Diagnosis

• Baseline investigations include serum prolactin as well as TSH and T4.
• In prolactinoma, prolactin is typically raised to more than five times normal and correlates with tumour size, whereas non-functioning masses usually do not raise prolactin above three to four times normal.
• Macroprolactin, a prolactin isoform of higher molecular weight and reduced bioactivity, can explain raised values without symptoms; with very large tumours and only modestly raised prolactin, a hook effect can produce falsely low values, revealed by dilution of the sample.
• Contrast-enhanced MRI of the pituitary demonstrates the adenoma, complemented by visual field testing in macroadenomas.

Keep learning in the app

Further reading (selection)

1. MSD Manual Professional: Prolactinoma
2. StatPearls: Prolactinoma (NCBI Bookshelf)
3. Approach to the Patient With Prolactinoma (J Clin Endocrinol Metab 2023, PubMed Central)
4. DocCheck Flexikon, Hyperprolaktinämie

Cross-references