High prolactin: how it stops ovulation

How does prolactin actually stop ovulation?

To see why prolactin matters for getting pregnant, it helps to look at the chain of signals your body relies on each cycle. Ovulation depends on a brain hormone called GnRH. GnRH tells your pituitary gland to release two other hormones, LH and FSH. Those two are what actually drive an egg to grow and release.

When prolactin is high, it blocks GnRH from being released. With less GnRH reaching the pituitary, LH and FSH drop too. The chain of signals that leads to ovulation never gets going. This is the core problem with high prolactin: it's not that it attacks your ovaries directly. It interrupts the communication line further up, at your brain and pituitary gland.

What prolactin level counts as too high?

There's no single fixed cutoff. But there are useful reference points. The average baseline prolactin level in women is around 13 ng/mL. Most labs consider anything above roughly 15 to 20 ng/mL to be elevated. This state is called hyperprolactinemia.

Because prolactin naturally rises and falls, when you're tested matters. For the most reliable result, blood should be drawn mid-morning, on an empty stomach. Both the time of day and recent eating can change the number. If your result comes back borderline, your provider may just ask you to repeat the test under these more controlled conditions before drawing any conclusions.

What usually causes high prolactin?

High prolactin isn't one condition with one cause. It's a lab finding that can point to a few different things, which is exactly why doctors investigate further.

An underactive thyroid is one recognized cause. When your thyroid isn't making enough hormone, your body increases a signal called TRH to try to compensate. That same signal also triggers prolactin release, raising your levels as a side effect.

Certain medications are another well-documented cause. These include some antipsychotics (like risperidone, haloperidol, and fluphenazine). They also include some antidepressants, such as older tricyclics and SSRIs. If you're on any of these, it's worth mentioning to your provider rather than assuming they're unrelated to a cycle change.

A physical cause is possible too. Prolactinomas are non-cancerous pituitary tumors made of prolactin-producing cells. They are a common finding behind high prolactin, making up to 40% of all pituitary tumors. The word "tumor" can sound scary. But prolactinomas are typically non-cancerous. As covered below, they usually respond well to medication.

What is galactorrhea, and does it mean something?

One physical sign specifically tied to prolactin is galactorrhea — unexpected milky discharge from the nipples outside of pregnancy or nursing. It's strongly linked to high prolactin. Most women who notice this symptom do turn out to have high prolactin when tested.

Not everyone with high prolactin notices this, and not noticing it doesn't rule anything out. But if you've seen it alongside irregular cycles, it's a specific detail worth bringing to your provider. It can help focus the workup instead of leaving things to a general "let's check everything" approach.

What does getting diagnosed actually involve?

The process starts simply: your provider orders a prolactin blood test, ideally drawn mid-morning and while fasting, for the most accurate reading.

If your prolactin does come back high, the next step is figuring out why. This may include a thyroid test, because of the hypothyroidism link. It may also include a review of your current medications. If a physical cause needs to be ruled out, an MRI of the pituitary gland with contrast dye is the preferred way to check for a prolactinoma. This step isn't automatic for every high result. Your provider decides whether it's needed based on your levels and overall picture.

How is high prolactin treated?

When treatment is needed, a class of medications called dopamine agonists is the standard approach. They work by restoring the dopamine signal that normally keeps prolactin in check. This then lets GnRH, LH, and FSH get back to their normal rhythm.

Among these medications, cabergoline is usually preferred. It tends to work better at bringing prolactin levels back to normal and, when a prolactinoma is present, at shrinking it.

If you get pregnant while being treated, and your provider decides treatment should continue, bromocriptine is typically the preferred choice during pregnancy. It has a better safety record for pregnancy than cabergoline. Any decision about starting, switching, or continuing treatment should always be made with your provider. They will base it on your levels, your specific cause, and your pregnancy plans.

Frequently asked questions

Sources

1. High prolactin suppresses fertility mechanistically by inhibiting the release of GnRH, which in turn reduces the pituitary's secretion of LH and FSH — the hormones that drive ovulation. — StatPearls (NCBI Bookshelf)
2. Normal baseline prolactin averages around 13 ng/mL in women, and most labs consider levels above roughly 15 to 20 ng/mL to be elevated (hyperprolactinemia). — StatPearls (NCBI Bookshelf)
3. Underactive thyroid (primary hypothyroidism) can raise prolactin levels because the elevated thyroid-stimulating hormone-releasing signal (TRH) that results also stimulates prolactin secretion. — StatPearls (NCBI Bookshelf)
4. Certain medications, including dopamine receptor-blocking antipsychotics (e.g., risperidone, haloperidol, fluphenazine) and antidepressants such as tricyclics and SSRIs, are recognized drug-related causes of elevated prolactin. — StatPearls (NCBI Bookshelf)
5. Prolactinomas — benign pituitary tumors of prolactin-producing cells — are a common structural cause of hyperprolactinemia, accounting for up to 40% of pituitary adenomas. — StatPearls (NCBI Bookshelf)
6. For accurate testing, prolactin blood levels should ideally be drawn in the mid-morning, in a fasting state, since timing and eating can affect results. — StatPearls (NCBI Bookshelf)
7. When elevated prolactin needs to be investigated for a structural cause, contrast-enhanced MRI of the pituitary is the preferred imaging test. — StatPearls (NCBI Bookshelf)
8. Among dopamine agonist medications used to treat hyperprolactinemia, cabergoline is generally favored over other options because it is more effective at normalizing prolactin levels and shrinking prolactin-secreting tumors. — StatPearls (NCBI Bookshelf)
9. If someone with hyperprolactinemia becomes pregnant and needs treatment continued, bromocriptine is the preferred dopamine agonist during pregnancy because it has more favorable safety data than cabergoline. — StatPearls (NCBI Bookshelf)
10. Galactorrhea (unexpected milky nipple discharge) is strongly linked to high prolactin — the large majority of women who have galactorrhea also turn out to have hyperprolactinemia. — ASRM / ReproductiveFacts.org
11. The diagnostic workup for suspected hyperprolactinemia starts simply, with a healthcare provider ordering a prolactin (PRL) blood test. — Cleveland Clinic