High prolactin in men and women. What does it affect?.

What is prolactin?

Prolactin is a hormone whose name comes from its function of stimulating milk production (lactation) in mammals. Increased serum prolactin levels during pregnancy cause the mammary glands to enlarge in order to produce milk. This process usually begins with a decrease in progesterone towards the end of pregnancy. The hormone also plays an important role in maternal behaviour (1). In addition, it has about 300 other functions in the body. These can be divided into several types: reproductive functions, metabolic functions, fluid regulation (osmoregulation), regulation of the immune system (immunoregulation) and behavioural functions (2).

In humans, prolactin is produced by lactotroph cells both in the anterior pituitary gland and in many other locations in the body. It is also stored in the pituitary gland and then released into the bloodstream. Human prolactin is furthermore produced, in small amounts, in the uterus, immune cells, brain, breast, prostate, skin and adipose tissue (3).

One of the main regulators of prolactin production from the pituitary is a hormone called dopamine, which is produced by the hypothalamus. Estrogen is another key regulator of prolactin - it increases the production and secretion of prolactin from the pituitary gland. In addition to these, a whole host of other hormones increase or decrease the amount of prolactin released in the body, some examples being thyrotropin-releasing hormone (thyreolysin), oxytocin and antidiuretic hormone (4).

The consequences of abnormal prolactin levels can be fertility disorders, both in women and men.

High prolactin levels in men and women - what does it mean?

If prolactin levels are higher than normal, this could mean that there is some type of pituitary tumour that is increasing the production of the hormone. Other possible causes are:

• hypothyroidism,
• polycystic ovary syndrome,
• medication for depression or psychosis,
• opioids,
• certain foods or herbs, including fenugreek or fennel seeds,
• irritation of the chest wall (caused by surgical scars, hemiplegia or even a bra that is too tight),
• stress,
• excessive physical exertion (5).

Elevated prolactin levels lowers sex hormone levels - oestrogen in women and testosterone in men. Its excess can also stimulate breast milk production in men and in women who are not pregnant. In addition, visual disturbances and headaches may be among the characteristic symptoms of the tumour (6). Other symptoms may result from a reduction in the production of other hormones by the pituitary gland as a result of tumour compression.

In women, too much prolactin can cause:

• irregular menstrual periods, their disappearance or lack of ovulation,
• painful intercourse due to vaginal dryness,
• breast pain,
• acne and excessive growth of body and facial hair (7).

This is vital information for aspiring and expectant mothers. Overproduction of the hormone can disrupt periods and lead to infertility. Prolactin is also very important during pregnancy so that the foetus can develop properly and the termination can take place without complications.

In men, higher prolactin levels can affect:  

• erectile dysfunction and testicular function,
• hypogonadism,
• decrease in libido,
• reduced body and facial hair,
• sometimes breast enlargement (8).

What tests should be performed with elevated prolactin?

The normal concentration of this hormone is 102 - 496 µIU/l in women who are not pregnant and 86 - 324 µIU/l in men. If the doctor suspects an elevated prolactin level, or hyperprolactinaemia, he will refer the patient for a blood test. Prolactin is determined in serum and the sample is taken from a vein, usually from the ulnar fossa. 

The test is best performed in the morning, on an empty stomach and after an undisturbed sleep of about 8 hours.

The test is best performed in the morning, on an empty stomach and after an undisturbed sleep of about 8 hours. Blood should not be taken after stressful situations or after breastfeeding, and abstinence from alcohol and intercourse is recommended the day before. It is very important to inform your doctor about any medication you are taking. Some of these may interfere with the results, such as contraceptive drugs, blood pressure medication or antidepressants.

In some cases, prolactin levels may be falsified, i.e. lower in the laboratory result than their true level in the case of very high serum prolactin concentrations (hook effect). This occurs because of the limitations of the method of testing prolactin levels (antibody saturation). In this case, patients have clear symptoms or abnormalities on imaging studies (pituitary macroadenoma), while levels are inadequately low or lower than expected. Another example is inadequately high prolactin levels in asymptomatic patients or those with discrete symptoms, in which case inactive conglomerates of so-called macroprolactin are detected. These situations require additional tests or appropriate preparation of the sample prior to testing.

Bibliography:

1. https://www.britannica.com/science/prolactin

2. https://www.hellozdrowie.pl/prolaktyna-normy-prawidlowe-ile-wynosza/

3. https://www.hormone.org/your-health-and-hormones/glands-and-hormones-a-to-z/hormones/prolactin

4. https://www.hormone.org/your-health-and-hormones/glands-and-hormones-a-to-z/hormones/prolactin

5. https://www.webmd.com/a-to-z-guides/prolactin-test

6. https://helloclue.com/articles/cycle-a-z/hyperprolactinemia-and-the-menstrual-cycle

7. https://www.webmd.com/a-to-z-guides/prolactin-test

Authorisation of content:

Grzegorz Ziółkowski, MD - specialist gynaecologist-obstetrician from the InviMed clinic in Warsaw (Praga)

The medical information presented should be considered as general guidelines and does not replace the individual judgement of the doctor regarding the medical management of each patient. The doctor, after a thorough examination of the patient's condition, determines the extent and frequency of diagnostic tests and/or therapeutic procedures, taking into account specific medical indications. All medical decisions are made in full consultation with the patient.

Author of the article

Invimed editorial team - we serve patients by solving their fertility problems. We use world medical knowledge, state-of-the-art technology and treatment methods. We are here to make dreams of parenthood come true. The smiles on the faces of happy parents give meaning to our work.

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