Prolactin
PRL· also: Prolactin
Clinical Overview
Prolactin is produced by the anterior pituitary and is the primary hormone responsible for milk production (lactation). Outside of pregnancy and breastfeeding, elevated prolactin (hyperprolactinemia) suppresses the hypothalamic-pituitary-gonadal axis, causing menstrual irregularities, infertility, and galactorrhea in women, and reduced libido, erectile dysfunction, and infertility in men.
Why This Test Matters
Hyperprolactinemia is one of the most common endocrine disorders causing secondary hypogonadism and infertility. The most important cause to exclude is a prolactinoma — a benign pituitary tumor that responds dramatically to dopamine agonist therapy (cabergoline, bromocriptine). Mild prolactin elevation (25–60 ng/mL) requires investigation of medications before imaging. Prolactin above 200 ng/mL almost always indicates a prolactinoma.
Reference RangesWHO/IFCC standards
| Age Group | Sex | Reference Range | Unit | Notes |
|---|---|---|---|---|
| Adults (18–64) | Female | 2 – 29 | ng/mL | Non-pregnant |
| Adults (18–64) | Male | 2 – 18 | ng/mL | — |
| All ages | Female | 10 – 300 | ng/mL | Pregnancy |
Also reported in: µg/L, mIU/L.
What Causes Abnormal Results?
High PRL Causes
- Prolactinoma (pituitary adenoma — most common pathological cause)
- Medications: antipsychotics (risperidone, haloperidol), metoclopramide, domperidone, SSRIs, opioids
- Hypothyroidism (TRH stimulates prolactin)
- Pregnancy and breastfeeding (physiological)
- Physical stress: chest wall surgery, nipple stimulation
- Chronic kidney disease
- Stalk effect (compression of the pituitary stalk by a non-prolactin tumor)
Low PRL Causes
- Pituitary failure (hypopituitarism)
- Medications: dopamine agonists (cabergoline)
Signs & Symptoms to Watch For
How to Prepare for This Test
Prolactin is best drawn 2–3 hours after waking (avoid early morning stress) in a fasting state. Breast stimulation and sexual activity should be avoided before testing. The sample should be collected after resting quietly for 20–30 minutes — stress and the venipuncture itself can raise prolactin transiently (stress prolactin).
Factors That Can Affect Results
- Stress and venipuncture (raises prolactin transiently)
- Sleep (prolactin peaks during sleep)
- Recent eating (postprandial rise)
- Medications (extensive list of drugs raise prolactin)
- Macroprolactin (high-molecular-weight prolactin that is inactive but measured by immunoassays — causes falsely elevated result without symptoms)
Related Topics
Frequently Asked Questions
What is macroprolactin and does it need treatment?
Macroprolactin is a complex of prolactin bound to IgG antibodies, forming a large molecule that is biologically inactive. It is detected by standard prolactin immunoassays, causing an apparently elevated prolactin result in an asymptomatic person. Macroprolactin can be identified by PEG precipitation — it constitutes >60% of total prolactin in macroprolactinemia. No treatment is needed, but the patient must be distinguished from someone with a true prolactinoma.
How is a prolactinoma treated?
Prolactinomas are treated primarily with dopamine agonists (cabergoline preferred over bromocriptine due to better tolerability and efficacy). Cabergoline normalizes prolactin in 80–90% of patients and shrinks the tumor in 75% of cases. Surgery (transsphenoidal adenomectomy) is reserved for patients intolerant of medication or with vision-threatening tumors. Radiation therapy is rarely used.