Prolactin

Prolactin is a hormone made by the pituitary gland, best known for its role in producing breast milk. Estrogen and some anti-androgens can raise it, so it is often on the list of blood tests for people on feminizing hormones.

Where you'll meet it

On feminizing blood test results, particularly for people taking cyproterone, which is more linked to raised prolactin than the other anti-androgens.

Why it is checked

A modest rise is common on feminizing hormones and usually means nothing. A level that keeps climbing can occasionally point to a prolactinoma, a benign growth on the pituitary gland. These are uncommon, and most are small and treatable with tablets, but they are the reason prescribers keep an eye on the number rather than ignore it.

Signs worth mentioning

Headaches that are new or persistent, changes in your vision, especially at the edges, or milky discharge from the nipples. None of these means something is wrong, but they are worth raising with your prescriber rather than waiting for the next routine test. A persistently high level usually leads to a repeat test, a look at the anti-androgen, and sometimes a referral to an endocrinologist or a scan.

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