Guide to Prolactin

WRITTEN BY

The Levels Team

Updated: 05/22/2025|12 min read

Summary

Prolactin is a hormone primarily produced by the pituitary gland, a small pea-sized gland at the base of the brain. While best known for stimulating milk production in pregnant and nursing women, prolactin affects many bodily functions in both women and men. 

Why It Matters

During pregnancy, prolactin levels gradually rise, preparing the breasts for milk production. After childbirth, prolactin levels surge when a baby nurses, triggering milk release. Beyond lactation, prolactin helps regulate the menstrual cycle by influencing estrogen and progesterone production. 

In men, prolactin contributes to reproductive health by influencing testosterone production and sperm development. While males produce much less prolactin than breastfeeding women, it still plays an important role in sexual function and fertility in men.

For both sexes, prolactin affects metabolism, bone density, and immune system function. It may also influence behavior, particularly parenting behaviors, though this is better understood in animals than humans.

Measuring prolactin in women helps diagnose causes of irregular or absent menstrual periods, unexplained milk production, fertility issues, and symptoms related to pituitary disorders. In men, prolactin testing can help evaluate causes of decreased libido, erectile dysfunction, low testosterone, and certain types of infertility.

Associated Symptoms

Prolactin levels themselves are laboratory findings rather than medical conditions. However, abnormal levels may be associated with various health conditions, each with their own symptoms.

Common symptoms that may indicate conditions associated with high prolactin in women:

• Irregular or absent menstrual periods: Prolactin can suppress the hormones responsible for ovulation and regular menstrual cycles
• Infertility: May be related to disrupted ovulation and hormonal imbalances caused by elevated prolactin
• Milk production when not pregnant or breastfeeding: Potentially caused by direct stimulation of breast tissue by excess prolactin
• Decreased sex drive: A potential result of prolactin's suppressive effect on estrogen and testosterone
• Vaginal dryness: Secondary to reduced estrogen levels, may be due to prolactin interference

Common symptoms that may indicate conditions associated with high prolactin in men:

• Decreased sex drive: May be due to prolactin's suppressive effect on testosterone production
• Erectile dysfunction: May be related to lowered testosterone and direct effects of prolactin on sexual function
• Infertility: Potentially a result of prolactin's negative impact on sperm production and testosterone levels
• Breast enlargement (gynecomastia): Can be a direct effect of prolactin on breast tissue combined with hormonal shifts
• Milk production: Direct stimulation of breast tissue may be due to excess prolactin, although rare in men

Low prolactin is uncommon and generally produces few direct symptoms except in nursing women, where it can cause insufficient milk production.

It's important to understand that many factors can cause these symptoms, and prolactin levels are just one piece of diagnostic information. The presence of symptoms alongside abnormal prolactin provides context for further investigation, but additional testing is typically needed to determine the underlying cause.

Clinical Ranges

Female:

• Non-Pregnant: 3.0-30.0 ng/mL
• Pregnant: 10.0-209.0 ng/mL
• Postmenopausal: 2.0-20.0 ng/mL

Male:

• 2.0-18.0 ng/mL

Lifestyle Factors That Can Impact It

Activities that may increase prolactin include:

• Frequent breast examinations or breast stimulation
• High-protein meals (if the degree of prolactin elevation is small, your provider may recommend repeating the test fasted)
• Excessive stress
• Physical activity (intense or prolonged)

Activities that may decrease prolactin include:

• Vitamin E supplementation (in some studies)
• Certain dietary adjustments (reducing protein intake if very high)

Other Factors That Can Impact It

Medical Conditions

• Pituitary tumors (prolactinomas): Dramatically increase prolactin through unregulated hormone production by tumor cells
• Trauma/ concussion: Temporary rise, from a change in blood flow to the pituitary
• Hypothyroidism: Raises prolactin because thyroid-stimulating hormone (TSH) indirectly stimulates prolactin release
• Chronic kidney disease: Increases prolactin due to decreased clearance of the hormone from the bloodstream
• Cirrhosis and liver disease: Elevate prolactin through impaired hormone metabolism and clearance
• Polycystic ovary syndrome (PCOS): Has associations with increased prolactin, but the causes are unclear
• Pregnancy: Progressively increases prolactin by design to prepare for lactation

Medications

• Antipsychotics: Increase prolactin by blocking dopamine, which normally inhibits prolactin release
• Certain antidepressants (particularly some selective serotonin reuptake inhibitors and tricyclic antidepressants): Raise prolactin through effects on serotonin and dopamine pathways
• Antihypertensives, such as methyldopa and reserpine: Can increase prolactin through central nervous system effects
• Opioids: May increase prolactin through effects on dopamine and endorphin systems
• Estrogens: Can increase prolactin through stimulation of lactotroph cells in the pituitary
• Dopamine agonists (bromocriptine, cabergoline): Dramatically decrease prolactin by mimicking dopamine's inhibitory effect on the pituitary gland
• Metoclopramide is a dopamine antagonist and can increase the prolactin level

Testing Accuracy and Stability

Prolactin testing can be influenced by several factors, requiring careful preparation and interpretation.

Factors That Can Affect the Accuracy of Your Test

• Recent stress can temporarily increase prolactin for several hours, potentially causing misleading results.
• Recent breast stimulation, including breast examination, can increase levels for 1--2 hours.
• Recent sexual activity may raise prolactin for up to 1--2 hours following orgasm.
• Sleep disruption the night before testing can affect morning levels, potentially increasing them if you slept poorly.
• Exercise within 12 hours of testing can temporarily elevate prolactin depending on intensity and duration.

How It Relates to Other Markers

Other tests can provide insights about health status when they're viewed alongside prolactin results. These tests may include:

• Thyroid-stimulating hormone (TSH): This hormone controls the functioning of your thyroid gland. It's essential to check this marker with elevated prolactin, as hypothyroidism can cause mild hyperprolactinemia (high prolactin), and can be reversible.
• Estrogen and testosterone: Prolactin affects and is affected by sex hormones. High prolactin can suppress these hormones, leading to reproductive symptoms.
• Luteinizing hormone (LH) and follicle-stimulating hormone (FSH): These reproductive hormones can be reduced when prolactin is high, helping explain fertility impacts.
• Cortisol: This stress hormone can increase alongside prolactin during stress responses.
• Kidney and liver function tests: These are important to review with unexplained prolactin elevation, as these organs clear prolactin from the bloodstream.
• Pregnancy test: This test is necessary to rule out pregnancy as a cause of elevated prolactin in women of reproductive age.

What Results May Mean in the Context of Other Markers

• High prolactin with high TSH: May suggest hypothyroidism as the cause of elevated prolactin---treating the thyroid condition often normalizes prolactin.
• High prolactin with low estrogen/testosterone: Can indicate hypogonadism due to prolactin suppression of the reproductive system.
• Very high prolactin (>100 ng/mL) with negative pregnancy test: May suggest prolactin-secreting tumor (prolactinoma).
• Mildly elevated prolactin with normal other hormones: Might reflect medication effect, stress-induced elevation, or idiopathic (unknown cause) hyperprolactinemia.
• High prolactin with high growth hormone or cortisol: May indicate a more complex pituitary tumor producing multiple hormones.
• High prolactin with kidney or liver dysfunction: May reflect reduced clearance rather than increased production of prolactin.

Follow-up Considerations

If your prolactin levels are abnormal, your provider may make some of the following recommendations. You should always speak to your doctor if you have medical questions or before making medical decisions.

When Re-Testing May Be Appropriate

• Initial mildly elevated result: Within 1--2 weeks, ideally in the morning after rest and fasting
• During medication treatment: Every 1--3 months initially, then every 6--12 months
• Monitoring known prolactinoma: Every 3--6 months, or as directed
• After medication adjustments: 2--4 weeks to assess impact
• During pregnancy with a history of prolactinoma: Each trimester
• Postpregnancy: 2--3 months after weaning to assess return to baseline

Additional Testing or Monitoring Your Doctor May Consider

• Pituitary MRI if significantly elevated prolactin
• Visual field testing if a pituitary tumor suspected
• Bone density scan with long-standing high prolactin
• Macroprolactin testing if asymptomatic with elevated prolactin (detects a benign form)
• Comprehensive metabolic panel
• Additional pituitary hormones if pituitary dysfunction suspected

When Additional Care May Be Warranted

• Very high prolactin levels (>100 ng/mL)
• Visual disturbances suggesting pituitary tumor pressure on optic nerves
• Severe or worsening headaches with elevated prolactin
• Infertility with abnormal prolactin
• Galactorrhea (milk production) when not pregnant or breastfeeding, or in men
• Inability to tolerate prescribed medications
• Pregnancy with a history of prolactinoma
• Bone density loss with chronic hyperprolactinemia
• Children or adolescents with elevated prolactin

Bibliography