Last Updated: OCTOBER 2023

Men with total testosterone below 300 ng/dL have 2.4 times higher cardiovascular mortality, as demonstrated in a 2018 study published in The Journal of Clinical Endocrinology & Metabolism. Understanding the intricate symphony of hormones is crucial for optimal male health, and while testosterone often takes center stage, other hormones like prolactin play a vital, often overlooked, role. Elevated prolactin levels, known as hyperprolactinemia, can complicate a man’s health picture and even mask the benefits of testosterone replacement therapy (TRT). Recognizing its symptoms and understanding its origins is key to effective endocrine management.

What is Prolactin and Why Does it Matter?

Prolactin is a hormone primarily produced by the pituitary gland, a small gland located at the base of your brain. While widely associated with lactation in women, prolactin also performs various functions in men, including modulating reproductive function, immune responses, and even mood. In men, normal prolactin levels are typically quite low, generally falling below 15 ng/mL. Some labs might use an upper limit of 20 ng/mL. Levels consistently above this threshold warrant investigation.

Prolactin’s Role in Men’s Health

High prolactin can directly impact a man’s reproductive health by suppressing the production of gonadotropin-releasing hormone (GnRH) from the hypothalamus, which in turn reduces the pituitary’s secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). This suppression leads to impaired testicular function and lower testosterone production, a condition known as hypogonadotropic hypogonadism. It’s crucial to understand that while TRT aims to restore testosterone, hyperprolactinemia often indicates a primary cause of low T, not a side effect of TRT itself.

When to Test Prolactin Levels on TRT

Testing prolactin is not a standard, weekly requirement for men on TRT. However, it is an essential baseline measurement before initiating TRT, and indicated if specific symptoms emerge or if a patient’s response to TRT is suboptimal despite achieving adequate testosterone levels. Comprehensive baseline lab work should always include prolactin, alongside total and free testosterone, estradiol (E2), LH, and FSH. As Dr. Jesse Mills highlights, monitoring pituitary markers like LH and FSH is important, and prolactin adds another layer to pituitary health assessment.

Symptoms of Elevated Prolactin in Men

Hyperprolactinemia can present with a range of symptoms, often mimicking or exacerbating symptoms of low testosterone. These include:

Sexual Dysfunction: Decreased libido, erectile dysfunction, and ejaculatory dysfunction.
Fertility Issues: Reduced sperm count and motility, leading to infertility.
Gynecomastia: Development of breast tissue, though less common than with high E2.
Galactorrhea: Spontaneous milky nipple discharge (rare in men, but possible).
Headaches and Visual Disturbances: Particularly if a pituitary tumor is present and growing.
Fatigue and Low Energy: Similar to symptoms of low testosterone.
Reduced Muscle Mass and Bone Density: Due to chronic hypogonadism.

If you experience these symptoms, especially if your TRT regimen is otherwise optimized (e.g., total testosterone 600-900 ng/dL, free testosterone 15-25 pg/mL, E2 20-40 pg/mL), it’s time to test your prolactin.

Causes of Hyperprolactinemia

Elevated prolactin can stem from various sources, categorized as physiological, pharmacological, or pathological.

Physiological Causes

Stress, intense exercise, sleep, and even nipple stimulation can cause temporary elevations in prolactin. Meals, particularly protein-rich ones, can also slightly increase levels.

Pharmacological Causes

Numerous medications can elevate prolactin:

Antipsychotics: Many conventional and atypical antipsychotics.
Antidepressants: Certain SSRIs and TCAs.
Opioids: Chronic opioid use is a significant cause.
Antihypertensives: Verapamil.
Prokinetics: Metoclopramide, domperidone.
Estrogens: Rarely used in men for TRT, but high endogenous E2 can sometimes influence prolactin.
H2 blockers: Cimetidine.

If you are on TRT and have elevated prolactin, your medication list should be meticulously reviewed.

Pathological Causes

The most concerning pathological cause of hyperprolactinemia is a pituitary adenoma, specifically a prolactinoma. These are benign tumors of the pituitary gland that overproduce prolactin. Other pathological causes include:

Hypothyroidism: Low thyroid hormone levels can increase TRH, which stimulates prolactin release.
Renal failure: Impaired prolactin clearance.
Liver disease: Affects hormone metabolism.
Chest wall injury or irritation: Herpes zoster, surgery, trauma.

Pituitary Considerations: Prolactinomas

Prolactinomas are the most common type of hormone-secreting pituitary tumor. They are almost always benign but can cause significant health issues due to both hormone overproduction and mass effect.

How Prolactinomas Manifest

Endocrine Effects: The primary effect is hyperprolactinemia, leading to hypogonadism (low LH/FSH and testosterone). This is often the initial reason a man seeks medical attention, perhaps for low libido or erectile dysfunction, before TRT is even considered.
Mass Effects: Larger tumors (macroprolactinomas, >10 mm) can press on surrounding structures, leading to:
- Headaches: Chronic or severe.
- Visual field defects: Compression of the optic chiasm, often causing bitemporal hemianopsia (loss of peripheral vision).
- Pituitary insufficiency: Compression of other pituitary cells, leading to deficiencies in other pituitary hormones (e.g., growth hormone, thyroid-stimulating hormone, ACTH).

Elevated prolactin levels, especially above 100 ng/mL, strongly suggest a prolactinoma, though values can be much higher (e.g., >200 ng/mL). Moderately elevated levels (25-100 ng/mL) are less specific and require careful differential diagnosis. If prolactin is significantly elevated, an MRI of the pituitary gland is typically warranted to visualize any potential tumor.

As stated in the Endocrine Society’s 2011 Clinical Practice Guideline for the Diagnosis and Management of Hyperprolactinemia: “Measurement of serum prolactin is indicated in patients with unexplained hypogonadism, erectile dysfunction, visual field defects, galactorrhea, or symptoms suggestive of a pituitary mass.” This reinforces the critical role of prolactin testing in men, especially when considering or managing hypogonadism.

TRT and Prolactin: Dispelling Myths

Testosterone replacement therapy itself does not cause hyperprolactinemia. In fact, some studies suggest that restoring testosterone to physiological levels can sometimes lower mildly elevated prolactin, particularly if the high prolactin was a secondary effect of hypogonadism rather than a primary pituitary issue. For example, a study by Vilar et al. (2014) published in Endocrine Connections observed a decrease in prolactin levels in some hypogonadal men after testosterone therapy.

Therefore, if hyperprolactinemia is diagnosed in a man on TRT, it is almost always an independent co-morbidity that needs to be addressed. It’s not a reason to stop TRT, but rather an indicator to investigate further for underlying causes such as a prolactinoma, medication side effect, or hypothyroidism.

Management of Hyperprolactinemia

Treatment for hyperprolactinemia depends on the underlying cause.

Medication Review: If a medication is suspected, an attempt to switch or reduce the dose may be made, under medical guidance.
Hypothyroidism Correction: If hypothyroidism is the cause, thyroid hormone replacement will usually normalize prolactin levels.
Dopamine Agonists: For prolactinomas, dopamine agonists like cabergoline or bromocriptine are the first-line treatment. These medications effectively suppress prolactin production and can shrink the tumor in most cases, often avoiding the need for surgery. Cabergoline is generally preferred due to its higher efficacy, longer half-life, and better tolerability.
Surgery/Radiation: These are reserved for cases unresponsive to medication, very large tumors causing significant mass effect, or those with acute vision compromise.

For men undergoing TR

Prolactin Levels on TRT: Understanding When to Test