A high prolactin level, called hyperprolactinemia, means your body is producing more of the hormone prolactin than expected. Normal levels fall below 20 ng/mL for men and below 25 ng/mL for nonpregnant women. When levels climb above those thresholds, it can signal anything from a medication side effect to a small pituitary gland growth, or it may simply reflect a temporary spike from stress or sleep. The cause matters because it determines whether you need treatment and what kind.
What Prolactin Does in Your Body
Prolactin is produced by the pituitary gland, a pea-sized structure at the base of your brain. Its primary job is stimulating breast milk production after childbirth, which is why prolactin levels climb dramatically during pregnancy (up to 500 ng/mL). Outside of pregnancy and breastfeeding, prolactin still circulates at low levels and plays a supporting role in reproductive hormone regulation. The pituitary keeps prolactin in check through a constant supply of dopamine, a brain chemical that acts as a brake on prolactin release. When that brake weakens for any reason, prolactin rises.
Common Causes of Elevated Prolactin
Prolactinomas and Pituitary Growths
The most common pathological cause is a prolactinoma, a benign tumor on the pituitary gland that overproduces prolactin. These are classified by size: microprolactinomas are smaller than 10 mm, macroprolactinomas are larger than 10 mm, and giant prolactinomas exceed 4 cm. Smaller tumors are far more common and typically respond well to medication. Larger ones can cause additional problems by pressing on nearby structures, particularly the optic nerve, which can affect peripheral vision.
Medications
Drug-induced hyperprolactinemia is extremely common and often overlooked. Because dopamine normally suppresses prolactin, any medication that blocks dopamine activity can let prolactin levels climb. The biggest offenders are antipsychotic medications, both older types like haloperidol and chlorpromazine, and newer ones like risperidone. Certain antidepressants can also raise prolactin, particularly SSRIs like sertraline, fluoxetine, and paroxetine, as well as some tricyclic antidepressants. Gastrointestinal medications used for nausea and motility, like metoclopramide and domperidone, are another frequent cause. Opiates, estrogen-containing medications, and some blood pressure drugs round out the list.
If you’re taking any of these medications and your blood work shows elevated prolactin, that connection is worth discussing with your provider before pursuing further testing.
Thyroid Problems
An underactive thyroid can raise prolactin through a chain reaction. When thyroid hormone drops, your brain produces more of a signaling hormone called TRH to try to stimulate the thyroid. TRH doesn’t just act on the thyroid, though. It also stimulates prolactin release from the pituitary. People with hypothyroidism sometimes develop milky breast discharge or menstrual irregularities that resolve once their thyroid condition is treated.
Temporary, Non-Medical Causes
Prolactin naturally fluctuates throughout the day. It rises during sleep, peaks in the early morning hours, and can spike temporarily from physical stress, vigorous exercise, nipple stimulation, sexual orgasm, chest wall irritation, a high-protein meal, or even the stress of having blood drawn. A single elevated reading doesn’t always mean something is wrong. Doctors typically confirm the finding with a repeat test, ideally drawn mid-morning while you’re relaxed and fasting.
Symptoms in Women
The hallmark symptoms in women revolve around reproductive disruption. High prolactin suppresses the hormones that drive your menstrual cycle, which can cause irregular periods or stop them entirely for three months or more. Without regular ovulation, fertility drops significantly. Some women also develop galactorrhea, a milky nipple discharge unrelated to pregnancy or breastfeeding.
Because prolactin suppresses estrogen, women with sustained high levels can experience symptoms that resemble menopause: hot flashes, night sweats, vaginal dryness, mood changes, low energy, difficulty concentrating, and reduced sex drive. These symptoms can appear well before the typical age of menopause and are sometimes the first clue that something is off.
Symptoms in Men
In men, elevated prolactin lowers testosterone. This can show up as reduced sex drive, erectile dysfunction, breast tissue enlargement, and in some cases, milky nipple discharge. Because testosterone drops gradually, men often attribute these changes to aging or stress and may not seek testing until a prolactinoma has grown large enough to cause headaches or vision changes. Infertility can also result, since low testosterone impairs sperm production.
Bone Loss: A Serious Long-Term Risk
One of the most significant consequences of untreated high prolactin is bone loss. Prolactin suppresses the reproductive hormones (estrogen in women, testosterone in men) that help maintain bone density. Over time, this leads to measurable thinning. In women with prolactinomas, studies have found cortical bone density drops by about 17% and the spongy inner bone (trabecular bone) drops by 15 to 30%.
The fracture risk is substantial. In one analysis, 46% of untreated women with prolactinomas had vertebral fractures compared to 20% of those receiving treatment. The pattern was even more pronounced in men: 67% of untreated men had vertebral fractures versus 26% of treated men. These numbers make a strong case that high prolactin isn’t something to simply monitor indefinitely without addressing the underlying cause.
How High Prolactin Is Treated
Treatment depends on the cause. If a medication is responsible, switching to an alternative that doesn’t affect dopamine often brings levels back to normal. If hypothyroidism is the culprit, treating the thyroid condition resolves the prolactin elevation on its own.
For prolactinomas, the first-line approach is medication rather than surgery. Dopamine agonists work by mimicking dopamine’s natural braking effect on the pituitary. They lower prolactin levels and, in most cases, shrink the tumor itself. Cabergoline is generally preferred because it’s taken just once or twice a week and tends to cause fewer side effects than the older alternative, bromocriptine, which requires daily dosing. Most people see prolactin levels normalize within weeks, and tumor shrinkage often follows over months. Surgery is reserved for the small number of cases that don’t respond to medication or where the tumor is causing urgent pressure on the optic nerve.
A Testing Quirk Worth Knowing
If you have a large pituitary tumor but your prolactin level comes back only mildly elevated (say, between 20 and 200 ng/mL), the result may be misleading. A phenomenon called the “hook effect” can cause lab assays to undercount prolactin when levels are extremely high, essentially overloading the test. Doctors can catch this by re-running the test on a diluted blood sample, which reveals the true, much higher level. This matters because a mildly elevated prolactin with a large tumor might be misattributed to the tumor pressing on the pituitary stalk rather than the tumor actively producing prolactin, and the treatment approach differs.
What Mildly Elevated Levels Mean
Not every elevated result points to a serious problem. Levels in the 25 to 50 ng/mL range are frequently caused by medications, stress, or the timing of the blood draw. Prolactinomas typically push levels higher, often well above 100 ng/mL for microprolactinomas and into the thousands for larger tumors. As a general rule, the higher the prolactin, the more likely a structural cause. But even modest, persistent elevations deserve follow-up if they’re accompanied by symptoms like menstrual changes, sexual dysfunction, or unexplained breast discharge.