Prolactin-producing pituitary tumour

A prolactin-producing pituitary tumour, also called a prolactinoma, is the most common type of hormone-making tumour in the pituitary gland. These growths are not cancerous and often respond well to treatment with medication, though some people may need surgery.

Table of contents

• What is a prolactin-producing pituitary tumour?
• Types and classification
• Symptoms
• Causes and risk factors
• Diagnosis
• Treatment
• Pregnancy and fertility
• Outlook and living with the condition

What is a prolactin-producing pituitary tumour?

A prolactin-producing pituitary tumour is a growth that develops in the pituitary gland (a small, pea-sized organ at the base of the brain) and makes too much of a hormone called prolactin^[1]. These tumours are also known as prolactinomas and represent the most common type of hormone-secreting pituitary tumour, accounting for up to 40% of all pituitary growths^[3].

The good news is that prolactinomas are not cancer. They are benign (non-cancerous) tumours that grow very slowly, and many do not seem to grow at all^[4]. While having a tumour near your brain can sound frightening, prolactinomas are not life-threatening. However, they can cause unwanted health problems, so it is important to seek care if symptoms develop^[2].

Prolactin is mainly responsible for breast milk production during pregnancy and breastfeeding. It also plays a role in the body’s reproductive system and other functions. When a prolactinoma causes the body to make too much prolactin, this condition is called hyperprolactinemia^[2].

prolactinoma, lactotroph adenoma, prolactin-secreting adenoma

Types and classification

Doctors classify prolactin-producing tumours based on their size. This matters because size affects both symptoms and treatment options^[2].

Microprolactinomas are very small tumours, less than 1 centimeter (about 3/8 of an inch) in diameter. These represent at least half of all prolactinoma cases and are more common in women. About 90% of women with prolactinomas have microprolactinomas^[3].

Macroprolactinomas are larger tumours, more than 1 centimeter in diameter. These are more common in men and tend to occur at an older age. About 60% of men with prolactinomas have macroprolactinomas^[3].

Some sources also mention giant prolactinomas, which are larger than 4 centimeters^[3].

Symptoms

A prolactinoma might not cause any symptoms at all. But when symptoms do occur, they can be caused by two things: too much prolactin in the blood, or the tumour pressing on nearby tissue^[1].

Too much prolactin can affect the reproductive system, a condition called hypogonadism. This leads to lower levels of sex hormones in the body. Because of this, some symptoms are different for women and men^[1].

Symptoms in women

Women often notice symptoms earlier than men, particularly changes related to menstrual periods or milky discharge from the breasts^[2]. Common symptoms in women include:

• Menstrual periods that are irregular or stop completely
• Milky discharge from the breasts when not pregnant or breastfeeding, called galactorrhea
• Sore or tender breasts
• Painful sex due to vaginal dryness
• Difficulty getting pregnant (infertility)
• Low interest in sex
• Acne and extra body and facial hair^[1]

Women taking hormonal medications like birth control pills or hormone replacement therapy may not experience these symptoms, which can lead to a delayed diagnosis^[2].

Symptoms in men

Men often have a delayed diagnosis because early symptoms may be less noticeable. Common symptoms in men include:

• Problems with erections (erectile dysfunction)
• Infertility
• Low interest in sex
• Less body and facial hair
• Smaller muscles
• Larger breasts, called gynecomastia^[1]

Symptoms from tumour size

If the prolactinoma is large (macroprolactinoma), it may press on nearby structures and cause additional symptoms:

• Headaches
• Vision problems, such as double vision or loss of side (peripheral) vision
• Nausea and vomiting
• Sinus pain or pressure
• Problems with sense of smell^[2]

Other effects

Left untreated, high prolactin levels can also lead to osteoporosis (weakening of the bones) or osteopenia (reduced bone density)^[2].

In children, prolactinomas are very rare but can cause delayed puberty^[2].

Causes and risk factors

Researchers do not know the exact cause of prolactin-producing pituitary tumours. Most cases happen randomly, without a clear reason^[2].

Prolactinomas develop from cells in the pituitary gland called lactotrophs that undergo changes and begin to multiply. Scientists have found that these tumours arise from a single cell that has undergone a genetic change (mutation). Some genes, such as the pituitary tumour transforming gene and a receptor for fibroblast growth factor 4, have been found in pituitary growths^[3].

While most prolactinomas occur by chance, certain genetic conditions can increase the risk, including:

• Multiple endocrine neoplasia (MEN) type 1: Between 15% and 60% of patients with MEN1 can have a pituitary growth, and the majority are prolactinomas^[3]
• Multiple endocrine neoplasia type 4
• Familial isolated pituitary adenomas (FIPA)^[2]

Who is at risk?

Prolactinomas can affect anyone, but certain groups are at higher risk. The mean prevalence is estimated to be about 10 per 100,000 in men and 30 per 100,000 in women. The highest number of cases occurs in women aged 25 to 34 years^[3].

It is important to note that not all cases of high prolactin are caused by a tumour. Other causes of elevated prolactin include pregnancy, certain medications (such as anti-nausea drugs or some antidepressants), an underactive thyroid gland, and pressure on the pituitary stalk from other types of tumours^[4].

• Pituitary gland
• Brain

Diagnosis

Diagnosing a prolactin-producing pituitary tumour requires specialized tests. Your healthcare provider will start with a physical exam and discussion of your medical history and symptoms. If you have milky nipple discharge, they may do a breast exam^[2].

Blood tests

The key test for diagnosing a prolactinoma is a blood test that measures prolactin levels. A normal prolactin level is less than 20 nanograms per milliliter. A prolactin level of more than 150-200 nanograms per milliliter usually signals a prolactinoma^[24].

Your doctor may also test other hormone levels to see if the pituitary gland is working correctly. For women who could be pregnant, a pregnancy test is typically done, as pregnancy naturally raises prolactin levels^[1].

Because prolactin levels can be affected by many factors, your doctor may need to do specialized blood tests to ensure an accurate reading^[24].

Brain imaging

If blood tests show high prolactin levels, your doctor will likely order imaging tests to look at the pituitary gland. The most common test is a magnetic resonance imaging (MRI) scan of the brain. This test can find a prolactinoma and show its size and exact location. If MRI is not available, a computed tomography (CT) scan may also be used^[1].

Vision tests

If the tumour is large, your doctor may recommend vision tests. These can show if the prolactinoma is affecting your sight, particularly your peripheral (side) vision^[1].

Other tests

Your healthcare team may also test for other conditions that can raise prolactin levels, such as an underactive thyroid gland or certain medications you may be taking^[4].

Treatment

The good news is that most prolactin-producing pituitary tumours can be successfully treated. The main goals of treatment are to lower prolactin levels back to normal, shrink the tumour, and help the pituitary gland work correctly^[9].

Some people with small prolactinomas that are not causing symptoms may not need treatment right away. Instead, doctors may recommend regular monitoring^[9].

Medication

For most people with prolactinomas, medication is the first and most effective treatment. Drugs called dopamine agonists are used to reduce prolactin production and shrink the tumour^[16].

The most commonly used dopamine agonists are:

• Cabergoline (brand name Dostinex): This is long-acting and usually taken once or twice per week. The usual dose is one tablet (0.5mg) once or twice weekly, though higher doses are sometimes needed^[11]
• Bromocriptine (brand name Parlodel): Usually taken two or three times daily (one 2.5mg tablet)^[11]
• Quinagolide (brand name Norprolac): Taken once daily, with the dose gradually increased to 75 micrograms^[11]

These medications work by mimicking the effects of dopamine, a brain chemical that controls how much prolactin the pituitary makes^[9].

Prolactin levels often fall to normal within a few weeks of starting treatment. In women, menstrual cycles usually resume and fertility is restored in most cases. In men, testosterone levels may rise, which often improves sex drive and potency. Nearly all prolactinomas shrink in size with medication^[11].

Side effects of medication

Most people tolerate these drugs well. To minimize side effects, particularly dizziness, nausea, and headaches, the medication should be taken with food. Cabergoline should be taken at night when going to bed with a light snack. Your doctor will give you instructions on how to build up the dose slowly to reduce side effects^[11].

Other possible side effects include:

• Tiredness
• Abdominal pain
• Breast discomfort
• Nasal congestion
• Constipation (usually improved by increasing fiber in your diet)^[11]

Rarely, high doses of dopamine agonists can trigger unusual behaviors such as pathological gambling or increased sexual interest. Patients and their families should be aware of this possibility and seek help from their doctor if they notice unusual behaviors^[11].

Some people can stop taking medication after 2 to 3 years, especially if their tumour was small when discovered. However, there is a risk that the tumour may grow and produce prolactin again. Other people need to take medication for life^[9].

Surgery

Surgery may be recommended in certain situations, such as when:

• Medication does not work or causes severe side effects
• The tumour does not respond to medication
• Symptoms are severe, such as sudden worsening of vision^[8]

The most common surgical approach is called transsphenoidal surgery, where the surgeon reaches the pituitary gland through the nose and sinuses. This is less invasive than traditional brain surgery and leads to an easier recovery. For larger tumours, a craniotomy (opening the skull) may be necessary^[16].

Sometimes medication is given before surgery to shrink the tumour and make it easier to remove^[16].

Radiation therapy

Radiation therapy is rarely used for prolactinomas. It may be considered when both medication and surgery have not worked, or if the tumour continues to grow or gets worse after other treatments. Radiation can be given as conventional radiation therapy or as stereotactic radiosurgery (also called gamma knife), which focuses high-powered radiation on a small area^[8].

Pregnancy and fertility

Having a prolactinoma can affect your ability to get pregnant because high prolactin levels interfere with the reproductive system. However, treatment with medication usually restores fertility^[11].

Before pregnancy

Fertility may return quite quickly after starting medication, so if you do not wish to become pregnant, you should discuss effective contraception with your doctor before treatment begins. If you wish to become pregnant, it is advisable to see your specialist for pre-pregnancy planning and advice^[11].

During pregnancy

Once pregnancy is confirmed, medication is normally discontinued, but you should seek advice from your specialist. You will continue to be monitored by your doctor throughout your pregnancy. Checking blood prolactin levels during pregnancy is not helpful since they rise naturally during normal pregnancy^[11].

A large prolactinoma can sometimes grow larger during pregnancy, though this is uncommon^[8].

There is good safety data for babies conceived while the mother is taking dopamine agonists^[11].

Breastfeeding

If you wish to breastfeed, you should discuss this with your specialist during pregnancy. Following birth, you will be reassessed regarding the need for further treatment^[11].

Outlook and living with the condition

The outlook for people with prolactin-producing pituitary tumours is usually excellent. Most prolactinomas respond well to medication, and many people can eventually stop treatment or need only low doses^[8].

Treatment for prolactinomas can change the levels of other hormones in the body, especially if surgery or radiation is performed. Getting tested regularly to check whether the tumour has returned after treatment is important^[8].

For people with small microprolactinomas, the tumour may not grow at all and may not require any specific treatment beyond monitoring. However, it is still important to follow up with your healthcare team as directed^[9].

Living with a prolactinoma means staying in regular contact with your healthcare team, taking medications as prescribed, and attending follow-up appointments. If you have a large tumour, you may need several brain scans over months and years to monitor how well the tumour is shrinking^[11].

While there is no scientific evidence that home remedies or dietary changes can shrink prolactinomas, maintaining good overall health habits may support your well-being during treatment. Some blogs claim that supplements or special diets can shrink tumours, but these claims are not based on medical evidence^[25].

If you experience new symptoms or side effects from medication, contact your healthcare team right away. They can adjust your treatment or provide additional support to help you manage your condition effectively.