What Is Prolactin and What Role Does It Play in the Body?

Prolactin is a polypeptide hormone (composed of several amino acids) secreted by the lactotroph cells of the anterior lobe of the pituitary gland, a small gland situated at the base of the brain. Prolactin production is regulated by dopamine produced by the hypothalamus. Its levels can vary depending on the time of day, stress, pregnancy, breastfeeding, or certain medical conditions. In general, reference ranges are between 100 and 500 mIU/L (i.e., 5 to 20 ng/ml) for women and between 85 and 325 mIU/L (i.e., 5 to 15 ng/ml) for men. Towards the end of pregnancy, a woman’s prolactin level can reach 250 ng/ml!

Whilst prolactin is mainly known for its central role in lactation, it is also involved in numerous physiological processes.

Stimulation of lactation

It contributes to the development of milk-producing cells in the breast during pregnancy. After childbirth, it triggers and maintains breast milk production in the mammary gland. It stimulates the biosynthesis of proteins, lipids, and carbohydrates in breast milk.

Regulation of the menstrual cycle

During breastfeeding, it acts as a natural barrier to a new pregnancy. It helps to suppress ovulation, which explains the absence of periods during this time. More specifically, it prevents the production of a hormone called GnRH, which is essential for producing two other hormones, FSH and LH, that trigger ovulation.

Effect on fertility

When prolactin inhibits the hormone GnRH outside periods of pregnancy and breastfeeding, it leads to problems with follicular maturation and irregular cycles, which can compromise embryo implantation.

Effect on growth

It affects the number of LH receptors in the testicles (from the onset of puberty) and in the ovaries (during the luteal phase, i.e., after ovulation). LH regulates testosterone production in men and stimulates ovarian follicles in women. During puberty, prolactin ensures the growth of the alveolar ducts, small channels in the breasts that drain milk.

Effect on libido

After orgasm, its levels in the blood rise sharply. This leads to a period during which sexual desire is temporarily suppressed, which is why arousal decreases following sexual intercourse. More generally, it influences the production of sex hormones (testosterone in men, oestrogen in women) that are essential for maintaining sexual desire.

• It enables the production and maintenance of breast milk after childbirth.

• It promotes the mother-child bond, particularly through breastfeeding.

• Helps to space out pregnancies by inhibiting ovulation whilst breastfeeding.

• Stimulates the development of the mammary glands at puberty and during pregnancy.

• Helps regulate libido and promotes a sense of well-being after orgasm in both men and women.

• It affects fertility in both men and women.

Hyperprolactinaemia refers to an abnormally high level of prolactin in the blood. This level is above 25 ng/ml in women and 15 ng/ml in men. Hyperprolactinaemia is normal and to be expected during pregnancy, breastfeeding, and when the nipples are stimulated by the newborn during feeds. Stress can also cause a temporary rise in prolactin l,evels in the blood, as can sleep, during which prolactin reaches its peak.

Hyperprolactinaemia can be problematic when it is caused by medication (certain antipsychotics, antidepressants or opioids) or by a medical condition (a benign pituitary tumour, certain kidney or liver diseases). These causes stimulate prolactin production, disrupt the mechanisms that control its release and affect health.

In women, hyperprolactinaemia can lead to:

• Disorders of the menstrual cycle or amenorrhoea, i.e., the absence of periods

• Galactorrhoea, i.e. the discharge of milk outside pregnancy and breastfeeding

• Vaginal pain or dryness

• Infertility issues, difficulty conceiving

• Weight gain

• A reduced sex drive

In men

• A reduced sex drive and erectile dysfunction

• Infertility problems

• More rarely, gynaecomastia, i.e., an increase in breast size

Note

Prolactin works by counteracting dopamine, a neurotransmitter that stimulates sexual desire. The higher the prolactin level, the more dopamine is suppressed, which reduces arousal and the desire for sexual intercourse.

The diagnosis of hyperprolactinaemia is based on a blood test that measures the level of prolactin in the blood. If the test shows an abnormally high level, the healthcare professional may request an MRI scan of the pituitary gland. The treatment prescribed then depends on the identified cause.

Several factors can influence this blood test:

• The time of day, particularly at night and upon waking

• Stress

• Intense physical activity

• Diet, particularly after a meal

Hyperprolactinaemia is defined as:

• Mild: 20 to 50 ng/ml.

• Moderate: 50 to 100 ng/ml.

• Severe: over 100 ng/ml.

• Very high, or even cause for concern, above 250 ng/ml (except in cases of pregnancy and breastfeeding).

Appropriate diet

To reduce hyperprolactinaemia naturally, it is best to limit galactogenic foods. Fennel, oats, sesame seeds, almonds, hazelnuts, cumin and basil are often recommended for breastfeeding women. It is best to avoid these, as well as alcohol – particularly beer, as the barley malt it contains increases prolactin secretion. 

Stress management

Chronic stress can lead to hyperprolactinaemia. Practices such as meditation, yoga, cardiac coherence or sophrology help to calm the mind. Physical exercise is also excellent for reducing stress. However, care should be taken not to exercise too intensely, as this could have the opposite effect on prolactin levels.

Dietary supplements and herbal medicine

• Vitamin B6: Helps regulate hormone levels and may help reduce prolactin production.

• Chaste tree: Helps regulate the menstrual cycle and prolactin production.

• Mucuna pruriens: Increases dopamine levels in the body, which inhibit prolactin.

If prolactin levels are too high, consult a healthcare professional. Hyperprolactinaemia can have many causes. A medical assessment can identify the exact cause, ensure no underlying condition is overlooked, and recommend appropriate treatment.

A blood test to measure prolactin levels may be carried out in women in the event of menstrual cycle disorders (absence of periods or irregular cycles), in the presence of abnormal milk discharge from the breasts, or when there are signs of oestrogen deficiency (reduced libido, vaginal dryness). In men, the test may be carried out in cases of erectile dysfunction or low libido, or if gynaecomastia (breast development) is observed. A test may also be requested in both men and women to investigate infertility.

With a dual background in literature and marketing, Hélène Durand uses her writing to explore topics that are meaningful to her: natural beauty, well-being, and a healthy lifestyle. Through her articles, she aims to share a supportive perspective and practical advice.