Prolactin (PRL) – BC254
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Sample Type: Blood (Serum)
Test Code: BC254
The Prolactin (PRL) test measures the level of prolactin, a hormone produced by the pituitary gland located at the base of the brain. While its primary function is to stimulate breast milk production (lactation) after childbirth, prolactin is present in both men and non-pregnant women, where it plays a significant role in regulating reproductive health and other hormones.
✔ A key investigation for causes of infertility in both men and women.
✔ Helps diagnose the reason for irregular menstrual cycles or the absence of periods (amenorrhea).
✔ Used to detect and monitor prolactinomas, which are benign tumors of the pituitary gland.
✔ Specific sample timing is crucial: collection should be in the morning, 3-4 hours after waking.
Prolactin: A Deep Dive into this Crucial Hormone
Prolactin is a vital hormone in the body's complex endocrine system. Its release is controlled by dopamine from the hypothalamus in the brain. In women, its levels rise dramatically during pregnancy and breastfeeding. However, in non-pregnant women and in men, prolactin levels should be relatively low. When levels are consistently high—a condition known as **Hyperprolactinemia**—it can significantly disrupt the normal function of the reproductive system. This is because high prolactin suppresses the secretion of Gonadotropin-releasing hormone (GnRH), which in turn reduces the production of Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH). This disruption is what leads to the common symptoms that prompt a doctor to order a prolactin test.
Symptoms that Warrant a Prolactin Test
A doctor will investigate your prolactin levels if you are experiencing:
Symptoms in Women:
- Menstrual Irregularities: Infrequent periods (oligomenorrhea) or a complete absence of periods for several months (amenorrhea).
- Infertility: High prolactin can prevent ovulation, making it difficult to conceive.
- Galactorrhea: A milky discharge from the nipples that is not related to pregnancy or breastfeeding.
- Decreased Libido: A noticeable drop in sexual desire.
Symptoms in Men:
- Decreased Libido: This is often one of the first and most common symptoms.
- Erectile Dysfunction: Difficulty achieving or maintaining an erection.
- Infertility: High prolactin can suppress testosterone production, leading to a low sperm count.
- Gynecomastia: A non-cancerous enlargement of the male breast tissue.
- Headaches or Vision Problems: If a large pituitary tumor (macroadenoma) is the cause, it can press on the optic nerves, causing these symptoms.
Understanding the Causes of High Prolactin (Hyperprolactinemia)
An elevated prolactin level can stem from a wide range of causes, which can be broadly categorized:
- Pathological Causes:
- Prolactinoma: This is the most common cause of pathological hyperprolactinemia. It is a benign (non-cancerous) tumor on the pituitary gland that autonomously secretes excess prolactin.
- Hypothyroidism: An underactive thyroid leads to increased levels of TRH (Thyrotropin-releasing hormone), which can also stimulate the pituitary to release prolactin.
- Systemic Disease: Chronic kidney disease (due to reduced clearance of prolactin) and severe liver disease can also lead to elevated levels.
- Polycystic Ovary Syndrome (PCOS): Mildly elevated prolactin is sometimes seen in women with PCOS.
- Pharmacological Causes (Drug-Induced):
- Many common medications can raise prolactin levels by interfering with the action of dopamine. These include certain antipsychotics, antidepressants (like SSRIs), anti-hypertensives (like verapamil), and opiates.
- Physiological Causes:
- These are normal, temporary increases. Prolactin levels naturally rise during pregnancy, breastfeeding, sleep, strenuous exercise, and in response to physical or emotional stress. This is why proper sample collection is so critical.
The Importance of Correct Sample Timing
To differentiate between a true pathological cause and a temporary physiological spike, the blood sample for a prolactin test must be collected under specific resting conditions. The ideal time is in the morning, approximately **3 to 4 hours after you have woken up**, and after a period of rest. This allows the levels that naturally peak during sleep to return to a stable baseline, providing your doctor with the most accurate and reliable result for diagnosis.
Frequently Asked Questions (FAQ)
The most common reasons are to investigate reproductive health issues. This includes infertility, irregular or absent periods, and milky nipple discharge in women, and low libido, erectile dysfunction, or infertility in men. It's also the main test to check for a pituitary gland tumor called a prolactinoma.
Prolactin levels have a natural daily rhythm, peaking during sleep and being highest right when you wake up. Waiting 3-4 hours allows these levels to settle to a stable baseline. This prevents a normal morning peak from being misinterpreted as a medical problem.
Not necessarily. While a pituitary tumor (prolactinoma) is a common cause, many other things can raise prolactin, including stress, an underactive thyroid, and numerous common medications. Your doctor will use the result to guide further investigation to find the specific cause.
No, fasting is not required. However, you should be well-rested and avoid heavy exercise or significant emotional stress right before the blood draw to ensure the result is accurate.