Prolactin is a pituitary hormone primarily known for lactation but with metabolic effects. Normal range: under 25 ng/mL in women; under 20 ng/mL in men (non-pregnant). Elevated prolactin can cause galactorrhea (milk production unrelated to childbirth), amenorrhea (menstrual loss), decreased libido, erectile dysfunction, infertility, vision changes (from large tumor), and headaches. Causes of elevated prolactin: prolactinoma (pituitary tumor — most common cause of significant elevation), medications (antipsychotics like risperidone and haloperidol — major cause; antidepressants, antiemetics like metoclopramide, blood pressure meds like verapamil and methyldopa, opioids), hypothyroidism (TRH stimulates prolactin), pregnancy/breastfeeding (physiological), stress (modest elevation), macroprolactinemia (large prolactin molecules with reduced activity — test artifact), renal disease, liver disease. Connections to diabetes: prolactinoma may cause insulin resistance; antipsychotic medications cause both hyperprolactinemia and metabolic side effects (weight gain, diabetes risk); hyperprolactinemia causes hypogonadism affecting insulin sensitivity; direct metabolic effects modest. Treatment of prolactinoma (dopamine agonists like cabergoline) may improve insulin sensitivity. For most adults with diabetes, prolactin testing not routine. Tested when: hyperprolactinemia symptoms (galactorrhea, amenorrhea, ED, infertility), suspected pituitary tumor, evaluation of antipsychotic side effects. Treatment: dopamine agonists (cabergoline first-line) for prolactinomas — shrinks tumor and lowers prolactin in 80-90% of cases; surgery for tumors not responding to medication.
Prolactin Reference Ranges
| Group | Normal Range (ng/mL) |
|---|---|
| Non-pregnant women | under 25 |
| Pregnant women | 20-400 (increases through pregnancy) |
| Postpartum/breastfeeding | 50-300+ |
| Men (non-elderly) | under 20 |
| Elderly men | up to 25-30 |
| Children | under 20 |
| Microprolactinoma | often 50-200 |
| Macroprolactinoma (large tumor) | often over 200 |
Causes of Elevated Prolactin
- Prolactinoma: pituitary tumor producing prolactin; most common cause of significant elevation.
- Medications (major cause): antipsychotics (risperidone, haloperidol, fluphenazine), antidepressants (SSRIs occasionally), antiemetics (metoclopramide, prochlorperazine), blood pressure meds (verapamil, methyldopa), opioids, ranitidine (withdrawn).
- Hypothyroidism: TRH stimulates prolactin.
- Pregnancy and breastfeeding: physiological.
- Stress: modest elevation.
- Sleep, nipple stimulation: physiological.
- Macroprolactinemia: test artifact; benign.
- Renal disease: reduced clearance.
- Liver disease.
- Severe stress, vigorous exercise: temporary elevation.
- Polycystic ovary syndrome: modest elevation in some.
Symptoms of Hyperprolactinemia
- Women: galactorrhea (milk production not related to childbirth), amenorrhea or oligomenorrhea (missing/irregular periods), decreased libido, infertility, vaginal dryness.
- Men: decreased libido, erectile dysfunction, decreased sperm count, infertility, gynecomastia, occasionally galactorrhea.
- Both: headaches, vision changes (if large pituitary tumor), bone density loss with chronic untreated.
- Most adults with mild elevation are asymptomatic.
- Significant elevation (over 100): symptoms more common.
Connections to Diabetes
- Antipsychotic medications cause both hyperprolactinemia AND metabolic side effects (weight gain, diabetes).
- Adults with severe mental illness have higher diabetes rates partly from antipsychotic effects.
- Prolactinoma may cause insulin resistance.
- Hyperprolactinemia causes hypogonadism (low testosterone in men, low estrogen in women) — affects insulin sensitivity.
- Treatment with dopamine agonists may improve insulin sensitivity.
- Direct effects of prolactin on glucose metabolism modest.
Antipsychotics and Prolactin
- Many antipsychotics increase prolactin by blocking dopamine receptors.
- Highest prolactin elevation: risperidone, paliperidone, haloperidol, fluphenazine.
- Less prolactin elevation: olanzapine, quetiapine, clozapine.
- Minimal effect: aripiprazole (sometimes lowers).
- Sexual side effects from hyperprolactinemia.
- For adults with severe mental illness on antipsychotics: aripiprazole alternative for prolactin/sexual side effects.
- Discuss with prescriber if medication changes considered.
Prolactinoma Treatment
- Dopamine agonists (first-line): cabergoline (preferred — twice weekly), bromocriptine (older, more side effects).
- Shrink tumor in 80-90% of cases.
- Normalize prolactin in most.
- Side effects: nausea, headache, orthostatic hypotension.
- Cabergoline at high doses associated with cardiac valve issues — monitor with echo.
- Surgery: for adults not responding to medications.
- Radiation: for residual disease.
- Monitor with prolactin levels and MRI.
- Long-term endocrinology care.
When to Test Prolactin
- Galactorrhea (women without recent childbirth).
- Amenorrhea or irregular periods.
- Infertility evaluation.
- Erectile dysfunction or decreased libido.
- Suspected pituitary tumor (vision changes, persistent headaches).
- Antipsychotic medication side effects.
- Gynecomastia in men.
- Hypothyroidism diagnosis (test for prolactin too).
- Not routine for diabetes evaluation.
The Bottom Line
Prolactin is a pituitary hormone primarily known for lactation but with metabolic effects. Normal range: under 25 ng/mL in women; under 20 ng/mL in men (non-pregnant). Elevated prolactin can cause galactorrhea (milk production unrelated to childbirth), amenorrhea, decreased libido, erectile dysfunction, infertility, vision changes (large tumor), headaches. Causes of elevated prolactin: prolactinoma (pituitary tumor — most common cause of significant elevation), medications major cause (antipsychotics like risperidone and haloperidol; antidepressants; antiemetics like metoclopramide; blood pressure meds like verapamil and methyldopa; opioids), hypothyroidism (TRH stimulates prolactin), pregnancy/breastfeeding (physiological), stress, macroprolactinemia (test artifact; benign), renal disease, liver disease. Connections to diabetes: antipsychotic medications cause both hyperprolactinemia AND metabolic side effects (weight gain, diabetes); adults with severe mental illness have higher diabetes rates partly from antipsychotic effects. Prolactinoma may cause insulin resistance through hyperprolactinemia-induced hypogonadism affecting insulin sensitivity. Treatment with dopamine agonists may improve insulin sensitivity. Direct metabolic effects of prolactin modest. Testing: blood draw, ideally morning, after avoiding stress and physical activity. Repeat elevated levels — single elevation may not be meaningful. Symptoms in women: galactorrhea, amenorrhea/oligomenorrhea, decreased libido, infertility, vaginal dryness. Symptoms in men: decreased libido, erectile dysfunction, decreased sperm count, infertility, gynecomastia, occasional galactorrhea. Both: headaches, vision changes (large tumor), bone density loss with chronic untreated. Antipsychotics and prolactin: risperidone, paliperidone, haloperidol, fluphenazine cause highest elevation; aripiprazole minimal effect (sometimes lowers); aripiprazole alternative for adults with prolactin/sexual side effects on other antipsychotics. Prolactinoma treatment: dopamine agonists (first-line) — cabergoline (preferred, twice weekly) or bromocriptine; shrinks tumor in 80-90% of cases; normalizes prolactin in most. Side effects: nausea, headache, orthostatic hypotension; cabergoline at high doses associated with cardiac valve issues — monitor with echo. Surgery for non-responders. Long-term endocrinology care. For most adults with diabetes, prolactin testing not routine. Tested when: hyperprolactinemia symptoms (galactorrhea, amenorrhea, ED, infertility), suspected pituitary tumor (vision changes, persistent headaches), evaluation of antipsychotic side effects, gynecomastia in men, hypothyroidism diagnosis. See our broader diabetes detection guide for context.
