Prolactinoma - Symptoms, Causes, Diagnosis & Treatment

Hormonal imbalances can affect menstrual cycles, fertility, sexual health, and overall well-being. One possible cause is prolactinoma, a usually benign tumour of the pituitary gland that produces excess prolactin. This hormone plays an important role in breast milk production, particularly after childbirth.

Although prolactinomas are generally non-cancerous, untreated cases may affect reproductive hormones and, when the tumour grows large enough, cause headaches or vision problems. Recognising the symptoms and understanding the available diagnostic and treatment options can help people seek appropriate medical care.

Prolactinoma is a type of prolactin-secreting pituitary adenoma that develops in the pituitary gland at the base of the brain. It causes the gland to release excessive amounts of prolactin, leading to a condition known as hyperprolactinaemia.

The term prolactinoma refers to this hormone-producing tumour. Excess prolactin can interfere with the production of reproductive hormones, including oestrogen and testosterone. This may affect menstrual cycles, sexual function and fertility in both women and men.

Most prolactinomas are benign. However, their size, hormone production and effects on nearby structures determine whether treatment is necessary.

What Are the Symptoms of Prolactinoma?

The symptoms of prolactinoma vary depending on prolactin levels, tumour size, and the individual's hormonal status. Some people may not experience noticeable symptoms initially.

Prolactinoma Symptoms in Females

Common prolactinoma symptoms in females include:

• Irregular menstrual periods or absence of periods.
• Milky nipple discharge when not pregnant or breastfeeding, known as galactorrhoea.
• Difficulty becoming pregnant.
• Reduced sexual desire.
• Vaginal dryness or discomfort during sexual intercourse.
• Headaches or changes in peripheral vision when the tumour is large.

Symptoms of High Prolactin Levels in Males

Symptoms of high prolactin in men may include reduced sexual desire, erectile dysfunction, infertility, and low testosterone levels. Some individuals may also experience breast enlargement or, less commonly, milk production.

Persistent high prolactin levels can contribute to reduced bone density in both sexes. These symptoms can also occur due to other medical conditions, so clinical evaluation is important.

Prolactin Levels in Prolactinoma?

Prolactin levels in prolactinoma patients are often higher than the laboratory reference range. However, the results vary depending on tumour size, individual factors, and the testing method.

For many commonly used assays, the upper reference limit is approximately 20 ng/mL in men and 25 ng/mL in non-pregnant women. The appropriate reference range should always be taken from the laboratory report.

Prolactin levels may rise substantially in people with prolactinomas, but there is no single value that reliably determines tumour size or confirms the diagnosis in every case. Pregnancy, medications, hypothyroidism and other pituitary conditions can also affect the results.

Microprolactinoma

A microprolactinoma is a prolactin-producing pituitary tumour measuring less than 10 mm in diameter. It may cause menstrual irregularities, infertility or other symptoms associated with elevated prolactin.

Prolactin levels in microprolactinoma can range from mildly to substantially elevated. The level alone cannot establish the diagnosis, and results must be interpreted alongside symptoms, blood tests and imaging findings.

Macroprolactinoma

A macroprolactinoma measures 10 mm or more in diameter. These tumours may produce higher prolactin levels and can press on nearby structures, potentially causing headaches or visual disturbances.

Macroprolactinoma prolactin levels are often markedly elevated, although the relationship between tumour size and measured hormone levels is not always straightforward. In very large prolactinomas, certain laboratory assay effects (such as the hook effect) can occasionally produce falsely low prolactin results, and repeat testing with sample dilution may be required.

How Is Prolactinoma Diagnosed?

Prolactinoma diagnosis involves assessing symptoms, measuring hormone levels, and examining the pituitary gland.

Common investigations include:

• Blood tests: A prolactin test measures the hormone concentration in the blood. Repeat testing may be recommended when results are borderline or affected by temporary factors.
• Additional hormone tests: Thyroid function and other pituitary hormones may be assessed to identify alternative causes or related hormonal changes.
• MRI scan: Magnetic resonance imaging helps identify the tumour and determine its size and location.
• Vision assessment: Visual field testing may be recommended when a tumour could be affecting the nerves responsible for sight.

Doctors may also review medications, pregnancy status where relevant, and other medical conditions before confirming the diagnosis.

What Is the Treatment for Prolactinoma?

Prolactinoma treatment aims to lower prolactin levels, reduce tumour size, restore hormonal function, and relieve symptoms.

Medication: Dopamine agonists, such as cabergoline and bromocriptine, are commonly used. These medicines reduce prolactin production and often shrink the tumour. Treatment and monitoring depend on the individual's response and medical history.

Surgery: A transsphenoidal operation, commonly performed through the nose, may be considered when medication is ineffective, causes unacceptable side effects, or when specific tumour-related complications require surgical management.

Radiation therapy: This is rarely needed and may be considered in selected cases when other treatments have not adequately controlled the tumour.

Some small, asymptomatic tumours may be monitored rather than treated immediately. Regular medical follow-up is important to assess prolactin levels, tumour size and pituitary function. People who are pregnant or planning pregnancy should discuss treatment and monitoring with their endocrinologist.

Reader Information: This article is intended for general awareness and does not replace professional medical advice, diagnosis or treatment. Consult a qualified healthcare professional if you experience symptoms associated with elevated prolactin levels. An endocrinologist can assess a suspected prolactinoma, interpret hormone test results, and recommend appropriate treatment based on tumour size, symptoms, and individual health needs.