What is Prolactin?
Prolactin (PRL) is a pituitary hormone that stimulates breast milk production in women after childbirth. It also supports the immune system, mental health, and metabolism in both sexes. To learn more about its roles and factors that control its secretion, read the first part of this series.
Prolactin Blood Test
When is It Ordered?
Pregnant and breastfeeding women will normally have high prolactin levels.
Abnormal levels in nonpregnant women and men can cause a number of symptoms, including abnormal nipple discharge and fertility issues. In women, it can result in irregular or missing periods. In men, it can also lead to erectile dysfunction or reduced libido .
Your doctor may order the test to find out if high or low prolactin is triggering your symptoms. The test may also screen for pituitary tumors and medical conditions with impaired dopamine signaling.
Prolactin can be a part of routine sex hormones workup, along with:
How to Prepare for the Test
Experts suggest doing a prolactin blood test 3-4 hours after waking up. Avoid breast stimulation, sexual intercourse, physical exams, and stress the day before and that morning. This also means that you shouldn’t have a breast exam right before the blood draw, a mistake that sometimes happens in busy doctors’ offices [2, 3, 4].
|Men||3-15 ng/mL (mcg/L)|
|Nonpregnant women||4-23 ng/mL (mcg/L)|
|Pregnant women||34-386 ng/mL (mcg/L)|
|Children||3.2-20 ng/mL (mcg/L)|
In women, prolactin slightly varies depending on the phase of the menstrual cycle. During pregnancy, levels increase and can reach up to 20x the normal values before childbirth .
On the other hand, prolactin levels remain constant in healthy men and slightly drop with aging. They may peak in response to stress and other factors discussed below .
High Prolactin Levels
- Breast and nipple stimulation
Medications, pituitary tumors, and other diseases can cause abnormal hyperprolactinemia, which may require medical attention .
1) Pregnancy and Breastfeeding
After childbirth, high prolactin enables women to make breast milk .
Once the nursing begins, suckling becomes the primary stimulus for prolactin secretion and maintains milk production; nipple and breast stimulation cause prolactin spikes during breastfeeding. Elevated prolactin also prevents ovulation and new pregnancies shortly after childbirth [14, 15, 16].
Our brain releases prolactin (PRL) in response to stress, and it’s a common cause of high prolactin, especially in men .
If you feel stressed during blood sampling, you PRL levels can transiently rise. This is known as stress-related hyperprolactinemia. To avoid it, doctors suggest taking multiple samples in complete rest .
3) Pituitary Tumors
Prolactinomas are prolactin-secreting tumors of the pituitary gland. Based on the tumor size, the two most common types are microprolactinoma (<10 mm) and macroprolactinoma (> 10 mm). Doctors still don’t know the exact cause of these benign tumors .
Expected blood prolactin levels in prolactinoma are over 250 ng/mL. A person may also experience headaches and vision problems if the tumor is pressing on certain brain areas. A doctor will suggest a CT or MRI scan to confirm or exclude this condition .
Most prolactinomas respond well to drugs that block prolactin secretion and don’t require chemotherapy or radiation. They are the most common disease-related cause of elevated PRL and usually affect younger women [19, 20].
4) Underactive Thyroid
Thyroid hormones normally work in a negative feedback loop that starts in the brain. TRH (from your hypothalamus) increases TSH and prolactin. TSH, in turn, increases thyroid hormones. To avoid their own excess, thyroid hormones will block TRH once they reach normal levels .
About 10-25% of people with elevated prolactin have macroprolactinemia; most of them are symptom-free and don’t require medical treatment .
- Haloperidol (Haldol)
- Chlorpromazine (Largactil, Thorazine)
- Thioridazine (Mellaril or Melleril)
- Risperidone (Risperdal)
Antipsychotics reduce dopamine activity in the brain (by blocking D2 receptors) .
- Estrogens (including birth control)
- Anti-androgens (cyproterone acetate/Diane)
- Nausea medications (metoclopramide)
- Blood pressure drugs (methyldopa, reserpine, and verapamil)
- Drugs for acid reflux (cimetidine and ranitidine)
If doctors suspect drug-induced hyperprolactinemia, they will suggest a medication replacement that won’t impact prolactin secretion.
The following conditions may also cause high prolactin:
- Irregular cycles
- Vaginal dryness
- Erectile dysfunction
- Bone and muscle loss
- Reduced beard growth
Most hyperprolactinemia symptoms in both sexes stem from suppressed sex hormones, a result of prolactin blocking GnRH.
1) Reduced Fertility
In women trying to conceive, high prolactin levels prevent ovulation, lower sex hormones, and reduce the chance of pregnancy. Prolactin-lowering treatment significantly increased estradiol in 32 infertile women [43, 44].
During pregnancy, abnormally high prolactin levels may increase the risk of spontaneous miscarriages.
In 352 pregnant women with this issue, a prolactin-lowering drug increased the chance of a successful pregnancy by 33%; women who miscarried had significantly higher PRL. A smaller study failed to confirm this connection [45, 46].
2) Weight Gain
Prolactin increases appetite and food intake by causing leptin resistance. This effect is meant to provide extra energy and nutrients during pregnancy, but it can happen in all conditions with high prolactin [47, 48, 49, 50].
A smaller study observed that many people with prolactinomas are obese. This time, however, changes in prolactin levels didn’t impact weight loss .
3) Autoimmune Diseases
- Hashimoto’s disease (thyroid)
- Rheumatoid arthritis
- Psoriasis and psoriatic arthritis
People with lupus frequently have high prolactin levels. The more their prolactin levels rise, the more severe symptoms they experience. The connection is particularly strong in pregnant women [60, 59, 61].
The female-dominant role of prolactin might also explain why women are more likely to suffer from autoimmune disease .
4) Mood Swings and Behavior
According to a review of clinical trials, high prolactin (PRL) increases the risk of anxiety and depression in both men and women. Lowering high PRL levels significantly improved the symptoms in some patients .
In 25 depressed patients, some symptoms – such as feelings of detachment – correlated with prolactin levels. However, two studies on 160 patients found no connection between this hormone and depression [67, 68, 69].
Molecules made by breaking prolactin into smaller bits (called vasoinhibins – more about them below) triggered anxiety and depression in rats .
High prolactin can make women hostile, probably as a means to protect their children at all costs. It doesn’t seem to have the same effect on men .
In summary, high prolactin disrupts mood and behavior, but the research is too limited to draw a conclusion.
5) Breast Cancer Risk
According to an observational trial with over 6K women, high prolactin levels can increase the risk of breast cancer by up to 50%. The connection was strongest for postmenopausal women with estrogen receptor-positive (ER+) and metastatic tumors .
6) Bone Loss
After childbirth, high prolactin increases PTH to free calcium from the bones, making it available for breast milk production. In cases of chronic hyperprolactinemia, this may lead to bone loss and increase the risk of fractures in both sexes [75, 76, 77].
According to 2 smaller clinical trials (56 patients), high prolactin (150 ng/mL) may trigger migraine attacks. Prolactin-lowering treatment improved the symptoms and reduced migraine frequency in some patients [78, 79].
8) Blood Pressure and Heart Disease
Our body cuts prolactin molecules into vasoinhibins, smaller peptides that reduce the growth and leakiness of blood vessels .
Hyperprolactinemia and oxidative stress increase vasoinhibins, impair blood vessel growth, and raise the risk of heart disease after pregnancy. Drugs that lower prolactin showed promising results in animals with this condition [81, 82].
According to a study on mice, excess vasoinhibins may also increase blood pressure by blocking the production of nitric oxide .
However, some researchers have emphasized that vasoinhibins don’t always correlate with blood prolactin and suggested monitoring their levels directly .
An observational study on over 7K subjects investigated the impact of hyperprolactinemia on overall mortality. Researchers found a link between an increased risk of death and high prolactin (>47 ng/mL) caused by :
- Larger prolactin-secreting tumors (smaller ones didn’t impact it)
However, they pointed out that high prolactin has no direct effect on someone’s chance of dying. Instead, the underlying disease likely has an impact.
Patients with drug-induced hyperprolactinemia also had a higher risk of:
- Heart disease
- Bone fractures
How to Lower Prolactin Naturally
Supplements that may lower prolactin levels and thus boost fertility and libido include:
- Chaste tree (Vitex agnus-castus) 
- Mucuna [87, 88]
- Ginseng 
- Glutamine + Uridine/Cytidine 
- Ginkgo 
- Gamma oryzanol [92, 93]
- Vitamin E 
- Zinc 
- Ashwagandha 
Make sure to consult with your doctor before taking any drug or nutritional supplement.
Low Prolactin Levels
Abnormally low prolactin levels (hypoprolactinemia) are rare and usually don’t require medical attention .
2) Pituitary Disorders
Underactive pituitary gland (hypopituitarism) is another common cause of low prolactin .
Primary hypopituitarism is a rare condition with decreased production of prolactin, growth hormone and sex hormones. It delays growth and sexual development in children and causes premature aging in adults [110, 111].
Sheehan syndrome is another pituitary disorder that drops prolactin. It may occur due to massive blood loss during childbirth, which cuts the blood supply to the pituitary gland .
Signs and Symptoms
- Erectile dysfunction
- Reduced libido
- Premature ejaculation
- Metabolic syndrome
Low prolactin levels may also suppress your immune system .
How to Increase Prolactin Naturally
Women with inadequate lactation often seek natural ways to boost prolactin. Supplements that stimulate milk production (galactagogues) include:
- Intimate contact with her baby
- Hearing the baby cry for food
- Loving thoughts about the baby
- Support and comfort from her environment
In rare cases, low prolactin may have serious consequences such as infertility and thus require medical attention.
Stress, pituitary tumors, low thyroid hormones, and schizophrenia treatment can excessively raise prolactin levels. Symptoms include nipple discharge, low libido, infertility, irregular cycles, weight gain, mood swings, and migraines.
Lower your levels with supplements (such as chaste tree, mucuna, and zinc) and get more dietary protein and healthy fats.
High prolactin levels (>25 ng/mL) normally occur during pregnancy and breastfeeding. Women with low prolactin after childbirth don’t produce enough breast milk. Herbal supplements, a supportive environment, and intimate contact can increase milk production.
Low prolactin levels may also be due to certain medications or pituitary disorders, which can lead to sexual dysfunction and poor immunity.