Prolactin Test: Purpose, Procedure & Understanding Abnormal Levels



Summary

The Prolactin Test (PRL test) measures the level of prolactin, a hormone produced by the pituitary gland, located at the base of the brain. Prolactin plays a vital role in breast development during pregnancy and milk production after childbirth.
Normally, prolactin levels remain low in men and non-pregnant women. However, abnormally high levels — a condition known as hyperprolactinemia — may indicate pituitary gland disorders, hormonal imbalances, or certain medic

al conditions such as hypothyroidism or kidney disease.
This test helps identify underlying causes of infertility, menstrual irregularities, low libido, or galactorrhea (milk secretion in non-lactating individuals).

What Is a Prolactin Test?

A prolactin blood test evaluates the amount of prolactin hormone circulating in your bloodstream.

  • Produced by: Pituitary gland (the body’s “master gland”)
  • Main function: Stimulates breast tissue growth and milk production in new mothers
  • Also affects: Reproductive health, sexual function, and hormone balance in both men and women

When prolactin levels are too high, it can interfere with the normal function of the ovaries in women and testes in men, leading to infertility and other symptoms.

Why Is the Prolactin Test Done?

Doctors usually recommend a prolactin test to:

  • Diagnose a prolactinoma (a noncancerous pituitary tumor)
  • Investigate irregular or absent menstrual cycles
  • Determine the cause of infertility in men or women
  • Evaluate erectile dysfunction or low sex drive in men
  • Monitor response to treatment for pituitary tumors

When Should You Get Tested?

In Women:

  • Missed or irregular menstrual cycles
  • Milk production without pregnancy or breastfeeding
  • Nipple discharge
  • Infertility

In Men:

  • Erectile dysfunction (impotence)
  • Reduced sexual desire
  • Breast enlargement (gynecomastia)
  • Nipple discharge
  • Decreased body or facial hair

If caused by a prolactinoma, symptoms like headaches, vision changes, and hormone deficiencies may also occur due to tumor pressure on nearby structures.

How Is the Test Performed?

A healthcare professional draws a small sample of blood from a vein in your arm.

  • The process takes less than five minutes.
  • You may feel a slight sting or pressure when the needle is inserted.

Test Preparation

  • Timing matters: The test is usually done 3–4 hours after waking up, as prolactin levels fluctuate during the day.
  • You may need to fast before the test (your doctor will advise).
  • Inform your healthcare provider about any medicines, supplements, or vitamins you’re taking — some may alter prolactin levels.

Do not stop taking prescribed medication without consulting your doctor.

Understanding Your Results

Prolactin Levels

Possible Cause / Condition

Normal

Healthy pituitary and hormone balance

Slightly Elevated

Stress, exercise, sexual activity, or certain medications

Moderately/Severely Elevated

Prolactinoma, hypothyroidism, pituitary tumor, kidney/liver disease, or PCOS

Low Levels (Rare)

Pituitary dysfunction, post-pregnancy milk insufficiency

Conditions Linked to Abnormal Prolactin Levels

  • Prolactinoma (most common cause)
  • Hypothyroidism (low thyroid hormone)
  • Kidney or liver disorders
  • Polycystic Ovary Syndrome (PCOS)
  • Hypothalamic diseases
  • Certain medications (antidepressants, antipsychotics, etc.)

Further Diagnostic Tests

If prolactin levels are elevated, your doctor may recommend:

  • MRI Scan: To detect pituitary tumors or gland enlargement
  • Thyroid Function Tests (TSH, T4): To check for hypothyroidism
  • Sex Hormone Tests (Testosterone, FSH, LH): To assess fertility issues
  • Eye Examination: To check for vision problems due to tumor pressure
  • Macroprolactin Test: To differentiate inactive (bound) prolactin from active hormone forms

Treatment for High Prolactin Levels

Treatment depends on the underlying cause:

  • Medications: Dopamine agonists like bromocriptine or cabergoline help lower prolactin and shrink tumors.
  • Surgery: For large or resistant pituitary tumors.
  • Thyroid Treatment: If due to hypothyroidism, treating the thyroid disorder can normalize prolactin.
  • Lifestyle Changes: Managing stress and reviewing medication use may also help.

When Slightly High Prolactin Isn’t a Concern

Mild elevations may be temporary due to:

  • Stress or anxiety
  • Vigorous exercise
  • High-protein diet
  • Sexual activity

Your doctor may recommend retesting after some time to confirm persistent elevation before starting treatment.

❓ FAQs on Prolactin Test

1. Why is my thyroid being tested with prolactin?
Because hypothyroidism can raise prolactin levels. Correcting thyroid imbalance often normalizes prolactin.

2. Can men have high prolactin levels?
Yes. In men, high prolactin can cause erectile dysfunction, low libido, infertility, and breast enlargement.

3. How are prolactinomas treated?
Most prolactinomas respond well to medications like cabergoline or bromocriptine. Surgery is considered only if the tumor doesn’t shrink or affects vision.

4. What is macroprolactinemia?
It’s a condition where prolactin binds to antibodies, forming inactive complexes. Lab testing helps identify this non-harmful form of elevated prolactin.

5. Can stress increase prolactin levels?
Yes, stress temporarily increases prolactin secretion — usually not a sign of disease unless levels stay persistently high.

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