16th September 2024

Prolactinomas

Prolactin, secreted by the anterior pituitary gland, is regulated by TRH and various physiological factors. This hormone increases after childbirth and in combination with oestrogen enables women to produce breast milk. Dopamine significantly inhibits prolactin, making dopamine agonists the first-line treatment for prolactin-related conditions, including prolactinomas. Prolactinomas are the most common pituitary tumours in multiple endocrine neoplasia type 1 (MEN1) syndrome.

High prolactin levels can stem from various causes, which must be identified to effectively treat the underlying condition.

Causes of hyperprolactinaemia

Clinical features

In women, elevated prolactin levels can cause amenorrhea, oligomenorrhea, breast enlargement, breast pain, hirsutism, and infertility. Men may experience gynaecomastia and impotence. Both may present with galactorrhoea and loss of libido.

Investigations

Diagnosing a prolactinoma involves elevated prolactin levels and MRI evidence of a pituitary mass. Macroadenomas are detectable, while microadenomas are often not visible. Prolactin levels help determine the aetiology.

• A prolactin level of 1000 – 3000 mU/l is likely to be medication induced, hypothyroidism and physiological reasons listed above.
• A prolactin level >3000 mU/l is suggestive of a microprolactinoma or medication induced.
• A prolactin level >6000 mU/l is indicative of a macroprolactinoma.

Generally, higher prolactin levels correlate with larger adenomas. Measuring TRH can also be helpful as it stimulates prolactin secretion.

Management

First-line treatment for both microprolactinomas and macroprolactinomas includes dopamine agonists such as cabergoline (first line) and bromocriptine. Transsphenoidal surgery is considered for patients who do not respond to medication or cannot tolerate it, especially those with psychiatric histories affected by dopamine agonists.

References

• Snyder P. High prolactin levels and prolactinomas (Beyond the Basics) [Internet]. Cooper D, Martin K, editors. UpToDate. 2023. Available from: https://www.uptodate.com/contents/high-prolactin-levels-and-prolactinomas-beyond-the-basics#H8
• Snyder P. Causes of hyperprolactinemia [Internet]. Cooper D, Martin K, editors. UpToDate. 2023. Available from: https://www.uptodate.com/contents/causes-of-hyperprolactinemia