Prolactin – What Kind of Hormone Is It?

Prolactin (PRL) is a hormone produced mainly by the pituitary gland. It is responsible for many vital biological functions in both women and men. Although it is most commonly associated with lactation, prolactin also affects the hormonal system, fertility, as well as mental health and immunity.

What Is Prolactin Responsible For?

Prolactin regulates, among others:

• milk production after childbirth,
• the menstrual cycle and estrogen levels in women,
• testosterone levels and sexual functions in men,
• the body's response to stress,
• immune system functioning.

Prolactin Test – When and How to Prepare?

The prolactin test is performed using a blood sample, on an empty stomach, preferably in the morning between 7:00 AM and 10:00 AM, at least 2 hours after waking up. Before the test, it is important to avoid stress and intense physical activity.

Prolactin Test – On Which Day of the Cycle Should It Be Done?

For women, the prolactin test should ideally be done between the 2nd and 5th day of the menstrual cycle. This allows for the most accurate results.

When Should You Get a Prolactin Test?

A prolactin test is recommended when the following occur:

• menstrual cycle disorders or absence of menstruation,
• difficulties getting pregnant,
• galactorrhea (nipple discharge outside the breastfeeding period) or lack of lactation after childbirth,
• headaches and vision problems,
• decreased libido, erectile dysfunction (in men),
• gynecomastia.

What Are Normal Prolactin Levels and How to Interpret the Results?

Prolactin Reference Ranges:

Prolactin reference values may vary depending on the laboratory performing the test. It is always important to consider the reference ranges provided alongside your results. These values can be determined based on the equipment used, analysis methods, and reagents applied.

Low Prolactin – Symptoms and Causes

Low prolactin levels (hypoprolactinemia) are relatively rare. This condition may indicate dysfunction of the pituitary gland, such as trauma, tumors, or diseases that reduce prolactin production. Symptoms of low prolactin are especially noticeable in women of reproductive age and may include:

• lack of lactation after childbirth,
• menstrual irregularities,
• fatigue,
• low fertility,
• weight gain.

In men, low prolactin may result in reduced libido and fertility issues.

High Prolactin (Hyperprolactinemia) – Symptoms and Possible Causes

Elevated prolactin levels may result from:

• pregnancy and breastfeeding,
• hypothyroidism,
• pituitary tumors (e.g., prolactinoma),
• stress,
• use of certain medications (antipsychotics, antiemetics, hormonal drugs).

Symptoms in Women:

• menstrual disorders – irregular cycles, overly long or short periods, or complete absence of menstruation,
• milk discharge from the breasts in women who are neither pregnant nor breastfeeding,
• breast pain and tenderness,
• decreased libido,
• difficulty getting pregnant due to ovulation disorders.

Symptoms in Men:

• erectile dysfunction,
• enlargement of breast glands (gynecomastia),
• loss of muscle mass,
• reduced libido.