Prolactin is a hormone that is best known for allowing pregnant and breastfeeding women to produce milk.  It also plays a role in many other functions throughout the body in both males and females.

Prolactin is not what your doctor would usually test. Even though it can tell you a lot about your general health. Now you can go to a lab and test it yourself to make sure your body is functioning optimally. Just plug in your test results into Lab Test Analyzer, and you will find all the information you need about prolactin and your values, such as if your prolactin levels are optimal. And if they are not, it will tell you how to get there, using evidence-based lifestyle, diet, and supplement tips!

What is Prolactin

Prolactin is a peptide hormone made by the pituitary gland and various other parts of the body. It is also referred to as the luteotropic hormone (luteotropin) and PRL. Prolactin is encoded by the PRL gene (R).

Primarily, prolactin is responsible for the stimulation of milk production in women (lactogenesis) (R).

When a woman is pregnant, prolactin levels increase by up to 10-20 times the normal amount.  The levels return to normal within a few weeks after the mother stops breastfeeding.

Despite what its name suggests, prolactin does much more than only promote lactation. It is found in men as well and is influential in over 300 separate processes.  It is recognized as a multipurpose hormone with one of the widest ranges of physiological actions of any hormone (R).

Prolactin is important for water/salt regulation, metabolism, reproductive behavior, the immune system, hormones, and the brain (R).

Functions of Prolactin

1) Prolactin Helps Create Breast Milk

Milk production occurs after birth by allowing prolactin levels to remain elevated while progesterone and estrogen undergo an abrupt drop as they are rapidly cleared in 3-4 days after birth from the body. Estradiol acts at the hypothalamic level to increase prolactin secretion (R).

In the process of milk production, prolactin, along with cortisol and insulin, act together to stimulate genes that encode milk proteins.

Together, they stimulate the uptake of various amino acids and glucose, and the synthesis of the milk proteins (casein), fats, sugar (lactose), spermidine, and phospholipids, which are required for milk production. Non-pregnant levels of prolactin are sufficient to maintain milk production (R, R).

In breastfeeding mothers, prolactin is mainly secreted in response to stimulation of the nipples and breast by a suckling infant.  The suckling by the baby blocks the secretion of hypothalamic dopamine (which normally inhibits prolactin). This results in a sharp rise in prolactin concentrations in the blood, followed by a prompt fall when feeding stops (R).

The suckling activates mechanoreceptors in and around the nipple and these signals are carried by nerve fibers through the spinal cord to the hypothalamus (R).

High prolactin can cause bone loss in order to export calcium to breast milk (R, R, R, R, R).

Biochemically, prolactin activates the Jak2/STAT5 pathway, which is responsible for milk production.

2) Prolactin Plays a Role in Breast Development

Prolactin is merely a player in an orchestra of hormones and growth factors that support breast development (R).

Normal breast development requires prolactin, estrogen, progesterone, growth hormone, insulin, cortisolthyroid and parathyroid hormoneIGF-1, and EGF.  All of these together result in a functional gland.

Increased concentrations of prolactin in the blood during pregnancy cause enlargement of the mammary glands in order to prepare for milk production (R).

3) Prolactin Makes You More Nurturing and Influences Sexual Desire

In humans, high prolactin levels are associated with nurturing and parenting behaviors, as well as psychosomatic reactions including false pregnancy (R).

Prolactin may have a role in paternal care as well (in fish and birds).  In species where the male plays some role in the rearing of the offspring (rats), including humans, studies have found an association between prolactin and paternal care (R, R).

In women, prolactin can both increase or decrease sexual desire, and this depends on various factors.  In men, prolactin suppresses sexual behavior in rats (R).

4) Prolactin Helps Fetal Brain Development

Prolactin stimulates the growth, development, and metabolism of the fetus.  It also stimulates the formation of myelin coatings on axons in the brain (R).

Prolactin promotes neurogenesis in the mother and her fetus, immune tolerance of the fetus during pregnancy and contributes to the development of the fetal lungs (R).

5) Prolactin Helps Fertility (sometimes)

Since prolactin increases progesterone, it helps to sustain pregnancies (R, R).

However, unusually high levels during pregnancy are associated with spontaneous abortion (R, R).

Thus, high prolactin concentrations during breastfeeding reduce fertility, protecting women from a premature pregnancy (R).

At lower levels, prolactin can contribute to male fertility in mice (R), but high prolactin causes infertility in males.  It can also cause low testosterone, a lack of sexual desire, or erectile dysfunction (R).

Prolactin Affects Other Hormones

Elevated levels of prolactin decrease the levels of estrogen in women and testosterone in men. The effects of altered levels of prolactin on sex hormones are much more profound in women, substantially increasing or decreasing estrogen levels (R).

High prolactin concentrations inhibit secretion of GnRH, thereby decreasing luteinizing hormone and follicle-stimulating hormone (R).

Normal levels of prolactin in males enhance testosterone secretion and the creation of sperm (R).

Prolactin decreases hepcidin, which can increase blood iron levels (R).

Prolactin indirectly leads to the release Parathyroid hormone-related peptide (PTHrP) (via increasing serotonin synthesis in breasts), causing bone loss (R).

Normal Levels of Prolactin

You can request from your doctor to test your prolactin. Conventional doctors will look at high or low prolactin levels and not mention anything, but these can indicate that certain processes in the body aren’t optimal. This is why you need to put your results in Lab Test Analyzer, to help you get your prolactin in the optimum range.

The upper threshold of normal prolactin is about 25 µg/L for women and 20 µg/L for men. Prolactin levels below 3 µg/L in women and 5 µg/L in men are considered too low. Prolactin levels may be checked as part of a sex hormone workup since elevated prolactin secretion can suppress the secretion of other hormones like FSH, GnRH, and sex hormones (R).

Ideal levels of prolactin for men are probably between 5-10 µg/L.

Prolactin level blood tests are most accurate if conducted during the midmorning and not after stress, breast stimulation, physical examination, or other prolactin-increasing stimuli. In addition, elevated levels of prolactin should always be rechecked due to the variability of secretion and inaccurate test readings (R).

Prolactin levels rise to start one hour after a person falls asleep until peak amounts are reached between 5:00 and 7:00 AM.  The lowest levels occur during the midmorning after waking (R).

Normal Prolactin Levels in the Blood:

Nonpregnant women4-23 nanograms per milliliter (ng/mL) or 4-23 micrograms per liter (mcg/L)
Men3-15 ng/mL or 3-15 mcg/L
Pregnant women34-386 ng/mL or 34-386 mcg/L
Children3.2-20 ng/mL or 3.2-20 mcg/L


High Levels of Prolactin

Higher levels of prolactin are found in pregnancy and breastfeeding (R).

High levels of prolactin in a woman may cause:

  • Abnormal nipple discharge
  • Infertility/Difficulty getting pregnant
  • Low estrogen and progesterone levels (R)
  • Difficulty getting a period
  • Tiredness
  • Headaches
  • Nausea
  • Dizziness
  • Vision problems

High prolactin in males can cause (R):

  • Infertility
  • Low testosterone
  • Low sexual desire
  • Erectile dysfunction

A small benign tumor (microprolactinoma) is found in the pituitary of over one-third of women with high levels of prolactin.

Low Levels of Prolactin in Men

Low prolactin is associated with ovary dysfunction in women.

In men low prolactin is associated with:

  • Low testosterone
  • Erectile dysfunction
  • Premature ejaculation
  • Low sperm count
  • Reduced sperm motility
  • Decreased function of seminal vesicles

In one study on low prolactin in men, normal sperm function was restored when prolactin levels were raised back to their correct values.

In mice without prolactin receptors, the hair cycle is disrupted such that shedding occurred earlier and there was a reduced duration of the telogen phase (R).

What Increases Prolactin

Prolactin levels are the highest during sleep, shortly after you wake up, and during times of physical or emotional stress.

In a study on female volunteers under hypnosis, prolactin surges resulted from rage or humiliating experiences, but not from the fantasy of nursing.  Interestingly, compared to single males, fathers generally have higher prolactin concentrations (R).

The most consistent stimulus for prolactin secretion in males is stress (R).

Production of the prolactin-receptor in the brain increases with age, exposure to estrogens, elevation in prolactin levels, and by contact with babies (R).

Conditions with increased prolactin:

  • Pregnancy
  • Stress
  • Depression
  • Ovulation
  • Trauma
  • Surgery
  • Tumors of the pituitary gland (prolactinomas)
  • Hypothyroidism
  • Kidney disease
  • Liver disease
  • Seizures
  • Antipsychotics (via blocking DRD2 receptors) (R).
  • Some drugs and medications

Activities that increase prolactin:

Hormones that increase prolactin:


  • Activating the serotonin receptors 5HT2A and 5HT2C

What Decreases Prolactin

Everyone is different, and our bodies can be complex. If you want to decrease your prolactin levels, it’s best to analyze them with Lab Test Analyzer. Our tool will compute, based on this and your other results, the best steps you can take that will bring you back to optimal.

Low prolactin can be caused by (R):

Hormones that decrease prolactin:

Supplements that decrease prolactin:


The primary Prolactin Inhibiting Factor (PIF) is the neurotransmitter dopamine.  When prolactin is produced, the secretion of dopamine increases as well, which then restricts prolactin production.

Treatment with dopamine or compounds that activate dopamine receptors suppresses prolactin secretion.

Estrogen & Progesterone

Studies have shown that increased levels of estrogen correlate to higher amounts of prolactin secretion.  This is confirmed by the fact that women have higher levels of prolactin in their blood during stages of pregnancy and their reproductive cycle when estrogen levels are higher too.

Estrogen enhances the growth of prolactin-producing cells, stimulates prolactin production directly, and suppresses the production of dopamine.

Progesterone increases and decreases prolactin, depending on the area of the body.

Prolactin: The Bad

Many of the metabolic and immune functions of prolactin can be observed in males, but some of the effects of prolactin might not be high enough to be significant (R).

1) Prolactin is an Immune Stimulant

Prolactin affects a large number of cytokine receptors (R) and acts in a cytokine-like manner, increasing the production of many immune system cells (R).

Prolactin is mostly an immune stimulant. The hormone plays a role in autoimmune diseases.

Some types of lymphocytes secrete prolactin and this allows for the production of more lymphocytes (R, R, R).  Lymphocytic prolactin plays a role in skin graft rejection (R).

Immune responses (B cell, T cell) in organisms are enhanced by prolactin (R).

Prolactin increases cytokine secretion and inhibits the suppressor effect of regulatory T (Treg) cells in healthy individuals (R).

Treg cells help create tolerance and an anti-inflammatory environment.

Prolactin stimulates T effector cells (not good for autoimmune) and increases IFNy secretion, which encourages an inflammatory environment and Treg cell malfunction (R).

However, prolactin deficiency can cause immunodeficiency (R).

Interestingly, mice without the prolactin gene fail to show significant abnormalities in immune responses.  As a result, prolactin has a modulatory role in several aspects of immune function but is not strictly required for these responses (R).

2) Prolactin Can Cause Autoimmune Disease

Excess prolactin is one of the important factors in the development and course of autoimmune diseases such as (R, R2):

  • Autoimmune thyroid disease
  • Alopecia (R)
  • Systemic lupus erythematosus (R)
  • Rheumatoid arthritis
  • Psoriasis (R)
  • Systemic sclerosis
  • Polymyalgia rheumatica
  • Sjogren’s syndrome – excess prolactin is diagnosed in nearly one-third of these patients
  • Psoriatic arthritis – Drugs that lower prolactin help and improve joint and skin symptoms (R).

3) Prolactin Can Cause Weight Gain and Hunger

Prolactin receptors are found in fat tissue, liver, pancreas and the brain (R).

In fat tissue, prolactin is essential in fat cell production. It also increases the secretion of leptin and inhibits adiponectin (R).

Prolactin promotes appetite and contributes to the rapid increase in food intake during pregnancy and nursing (R).

In the pancreas, it increases insulin secretion (from glucose) and glucose sensitivity (R). This helps prevent diabetes during pregnancy but can cause weight gain (R).

Prolactin also induces functional leptin resistance, which would contribute to increased food intake, potentially mediating the well-established leptin resistance of pregnancy (R).

Patients with high prolactin are prone to excessive weight gain, and normalization of prolactin levels using dopamine activators is associated with weight loss (R).

Interestingly, gene studies have revealed that a common variant adjacent to the prolactin gene is associated with obesity (R).

4-5) Prolactin Can Cause Anxiety and Depression

A byproduct of prolactin (vasoinhibins) causes depression and anxiety.

There is a correlation between prolactin and anxiety in men (R).

Prolactin levels in unipolar depressive patients are related to dissociative symptoms (R).

Prolactin may cause mood issues because of it regulates receptor potential thresholds, neuronal excitability and/or neurotransmission efficiency (R).

6) Prolactin May Worsen Migraines and Cause Pain

High prolactin may contribute to the pain in migraines, which can subside when given a drug to decrease prolactin (R).

Women who were given a drug to lower prolactin experienced improvement in their migraines (R).

7) Prolactin Inhibits Blood Vessel Growth

Prolactin increases vasoinhibins, which are known for their inhibiting effects on blood vessel growth, vasopermeability, and vasodilation (R).

Disturbances of the prolactin/vasoinhibin axis are associated with the development of retinal diseases, cardiac diseases, and diseases occurring during pregnancy (R).

8) Prolactin May Cause Cystic Fibrosis

Prolactin is one of the possible causes in cystic fibrosis (R).

9) Prolactin May Increase Cancer Risk

Prolactin may increase breast and prostate tumors (R).

Prolactin: The Good

Now that we went through all the bad aspects of prolactin, it’s important to understand that there are also good elements.

If you’re confused by all this information, Lab Test Analyzer is your digital health advisor that helps you understand your lab tests and makes recommendations based on your results.

1) Prolactin and Electrolyte Balance

Prolactin is responsible for fluid, sodium, chloride, and calcium transport across intestinal epithelial membranes (R).

Prolactin acts on the kidney to promote sodium, potassium, and water retention (R).

2) Prolactin Is an Important Hormone During Sex

Prolactin provides the body with sexual gratification after sexual acts.  The hormone counteracts the effect of dopamine, which is responsible for sexual arousal. This is thought to cause the sexual refractory period (R).

The amount of prolactin can be an indicator of the amount of sexual satisfaction and relaxation. Unusually high amounts are suspected to be responsible for impotence and loss of libido (R).

Prolactin levels have also been found to rise with use of the drug MDMA (Ecstasy) (R).

3) Prolactin Increases Neurogenesis

In rats, prolactin can induce neurogenesis in the subventricular zone and the dentate gyrus (R).

Where Prolactin is Found in the Body

  • Prolactin is found to be secreted from the uterus, placenta, immune cells, brain, breasts, prostate, skin, and fat tissue (R).
  • Prolactin receptors are present in the breasts, ovaries, pituitary glands, heart, lung, thymus, spleen, liver, pancreas, kidney, adrenal gland, uterus, skeletal muscle, skin, and areas of the brain (R).

Irregular Prolactin Levels?

If you have not yet tested your prolactin levels, I recommend that you ask your doctor to do it. If you already have your blood test results and you’re not sure what to make of them, you need to check out Lab Test Analyzer. It does all the heavy lifting for you. No need to do thousands of hours of research on what to make of your various blood tests.

People don’t realize that their blood test results contain a gold mine of information that’s waiting to be unearthed. Unfortunately, not everyone has the time or the inclination to sift through dozens of research papers.

It’s super-simple so that even if you don’t have any background in science, you will understand what your results mean and what you can do to get them in the optimal range.

Lab Test Analyzer gives you up-to-date scientific information about your lab results. In addition, you will get both lifestyle tips and natural solutions to help you optimize your health. You can also rely on our science-based Optimal Ranges to prevent potential health issues and maximize your overall well-being.

All of the content is backed by science and researched by a team of PhDs, professors, and scientists.

We’re all unique, so we deserve solutions that treat us that way.


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