Benign pituitary tumours are unusual growths that develop in the pituitary gland, a pea-sized organ at the base of the brain that controls many important body functions. While most of these tumours are not cancerous, they can still affect hormone levels and cause symptoms that impact daily life.

What Are Benign Pituitary Tumours?

A pituitary tumour is an abnormal growth of cells within the pituitary gland, which sits at the base of the brain just behind the nose. The pituitary gland is sometimes called the “master gland” because it makes hormones that control many other glands in the body, including the thyroid, adrenal glands, and reproductive organs. It releases hormones that regulate growth, metabolism, stress response, and reproduction.^[1]

Most pituitary tumours are benign, meaning they are not cancer. Another name for these noncancerous growths is pituitary adenomas. These tumours typically grow slowly, stay in the pituitary gland or the tissue around it, and usually don’t spread to other parts of the body. However, even though they are benign, they can cause problems by making too much or too little of certain hormones, or by growing large enough to press on nearby structures like the optic nerves.^[1]

While many people may never know they have a pituitary tumour because it causes no symptoms, some tumours can lead to serious health issues. The pituitary gland produces several important hormones, including growth hormone, thyroid-stimulating hormone, hormones that control reproduction, and hormones that help the body deal with stress. When a tumour affects the production of these hormones, it can cause changes throughout the entire body.^[2]

Epidemiology: How Common Are Benign Pituitary Tumours?

Pituitary adenomas are more common than many people realize. They make up about ten to fifteen percent of all tumours that develop within the skull. About seventy-seven out of every one hundred thousand people have a pituitary adenoma. However, researchers believe these tumours actually occur in as many as twenty percent of people at some point in their lives. The actual number is likely much higher than what gets diagnosed because many people with pituitary adenomas, especially small ones, never experience symptoms and therefore never seek medical care.^[2]

Small pituitary tumours are extremely common, present in up to ten percent of the general population. Most of these will never grow and do not cause any symptoms. Many are discovered accidentally during routine brain imaging done for other reasons and rarely require any treatment. Some experts have even estimated that nearly thirty percent of the population may develop or harbor pituitary tumours at some point, though the clinical significance varies greatly.^[4]

These tumours can occur at any age, but they are most common in people in their thirties or forties. Women are more likely to develop pituitary adenomas than men. The tumours can affect anyone regardless of their background, though certain genetic conditions can increase the risk of developing them.^[2]

Causes of Benign Pituitary Tumours

The exact cause of most pituitary adenomas remains unknown. Unlike many other health conditions, these tumours don’t appear to be caused by lifestyle factors, infections, or environmental exposures. They develop when cells in the pituitary gland begin to grow and divide abnormally, forming a mass of tissue. Scientists are still researching why this happens in some people and not others.^[3]

While the precise trigger for tumour development isn’t clear, researchers understand that these are not contagious conditions. You cannot catch a pituitary tumour from someone else, and you cannot spread it to others. The tumours develop spontaneously within an individual’s pituitary gland as a result of changes in the cells themselves.^[1]

Risk Factors for Developing Pituitary Tumours

Certain hereditary conditions can increase a person’s risk of developing pituitary tumours. These genetic syndromes are relatively rare, but people who have them face a higher likelihood of developing adenomas. The most common hereditary conditions associated with pituitary tumours include Multiple Endocrine Neoplasia Type 1, also known as MEN1 syndrome, Carney complex, and isolated familial acromegaly. These conditions are passed down through families and affect the endocrine system in various ways.^[6]

However, it’s important to understand that most people who develop pituitary adenomas do not have any of these genetic conditions. The vast majority of pituitary tumours occur sporadically in people with no family history of the condition. Having a risk factor doesn’t guarantee you will develop a tumour, and many people without any known risk factors do develop these growths.^[9]

Age and sex also play a role in who develops these tumours. As mentioned earlier, they’re most common in middle-aged adults and slightly more common in women than men. However, pituitary adenomas can develop at any age, including in children and elderly individuals, though this is less frequent.^[2]

Symptoms of Benign Pituitary Tumours

The symptoms of pituitary adenomas vary widely depending on several factors. Some people experience no symptoms at all, while others face significant health challenges. The symptoms depend on whether the tumour is large enough to press on nearby structures, and whether it produces excess hormones. Understanding these two categories of symptoms can help explain the diverse experiences of people with pituitary tumours.^[2]

Symptoms from Tumour Size and Pressure

Larger pituitary tumours, called macroadenomas (greater than ten millimeters), can press on structures near the pituitary gland. The most common structure affected is the optic chiasm, where the optic nerves from both eyes meet. When a tumour pushes on this area, it can cause vision problems. Typically, peripheral or side vision is affected first, but central vision and color vision can also be lost. This vision loss can become permanent if not treated, potentially affecting a person’s ability to drive or perform daily activities.^[5]

Headaches are another common symptom of larger pituitary tumours. These headaches result from the pressure the tumour places on surrounding structures or on the pituitary gland itself. The pain can vary in intensity and may be persistent or come and go.^[3]

In rare cases, a pituitary tumour can press on the pituitary gland itself, damaging it and causing it to produce too little of one or more hormones. This condition is called hypopituitarism. When hormone levels drop too low, people may feel ill, feverish, sluggish, or extremely fatigued. This can significantly impact quality of life and daily functioning.^[5]

Uncommonly, large tumours can cause double vision, abnormal eye movements, a large pupil, or droopy eyelids. These symptoms occur when the tumour grows into areas that affect the nerves controlling eye movement.^[5]

Symptoms from Hormone Production

Some pituitary tumours produce excess amounts of hormones, and these are called functioning or secreting adenomas. The symptoms depend entirely on which hormone is being overproduced. Each type of hormone causes distinct changes in the body when present in excess.^[2]

Tumours that produce too much prolactin can cause women’s breasts to make milk even when they are not pregnant or nursing. In men, high prolactin levels can cause loss of sex drive or lower sperm count, affecting fertility and relationships. These tumours may also cause irregular menstrual periods in women or lead to erectile dysfunction in men.^[3]

When tumours produce excess growth hormone, they can cause an abnormal increase in the size of the feet, hands, and head. This condition, called acromegaly, also leads to changes in facial appearance. The bones and soft tissues continue to grow even in adults, creating noticeable physical changes over time.^[5]

Tumours producing too much adrenocorticotropic hormone, or ACTH, lead to excessive cortisol production. This causes a condition called Cushing’s disease, which results in weight gain (especially around the midsection and face), high blood pressure, easy bruising, weak bones, mood changes, and increased blood sugar levels.^[6]

Less commonly, tumours may produce too much thyroid-stimulating hormone or hormones that control the reproductive system. These can cause symptoms related to an overactive thyroid or reproductive issues including irregular periods, infertility, or changes in sexual function.^[6]

Prevention of Pituitary Tumours

Unfortunately, there is currently no known way to prevent pituitary adenomas. Since the exact cause of most tumours remains unclear and they don’t appear to be linked to lifestyle factors, there are no specific prevention strategies that have been proven effective. Unlike some other health conditions, dietary changes, exercise, or avoiding certain substances will not prevent the development of pituitary tumours.^[1]

For people with hereditary syndromes that increase the risk of pituitary tumours, genetic counseling may be helpful. Understanding family history and undergoing regular monitoring can lead to earlier detection if a tumour does develop. However, this is surveillance rather than prevention, and it only applies to the small percentage of people with these genetic conditions.^[9]

The most important approach is awareness and early detection. Being familiar with potential symptoms and seeking medical attention if concerning signs develop can lead to earlier diagnosis and treatment, potentially preventing complications. Regular medical checkups and honest communication with healthcare providers about any unusual symptoms remain the best approach.^[5]

How Pituitary Tumours Affect the Body

Understanding how pituitary tumours affect the body requires understanding the normal function of the pituitary gland. This small gland acts as a control center for the endocrine system, the network of glands that produce hormones throughout the body. The pituitary releases hormones that tell other glands when to produce their own hormones, creating a carefully balanced system.^[4]

When a tumour develops in the pituitary gland, it can disrupt this balance in two main ways. First, if the tumour grows large enough, it can physically damage the normal pituitary tissue by compressing it. This compression prevents the healthy parts of the gland from working properly, leading to decreased hormone production. The result is that other glands throughout the body don’t receive the signals they need to function correctly.^[2]

Second, many pituitary tumours consist of cells that actively produce hormones, but unlike normal pituitary cells, they don’t respond to the body’s feedback mechanisms that usually keep hormone levels balanced. These functioning adenomas produce hormones continuously, regardless of whether the body needs them. The excess hormones then travel through the bloodstream, affecting organs and tissues throughout the entire body.^[6]

The physical presence of a larger tumour can affect nearby brain structures. The optic chiasm sits directly above the pituitary gland, which is why vision problems are so common with macroadenomas. As the tumour grows upward, it pushes against these nerve fibers, disrupting the transmission of visual information from the eyes to the brain. The pattern of vision loss often affects the outer edges of vision in both eyes because of the specific arrangement of nerve fibers at the optic chiasm.^[5]

Hormone imbalances caused by pituitary tumours create widespread effects because hormones act as chemical messengers throughout the body. When growth hormone is overproduced, for example, it doesn’t just cause growth of bones. It affects metabolism, insulin resistance, heart function, joint health, and even the appearance of skin. Similarly, excess cortisol from ACTH-producing tumours doesn’t just cause weight gain but affects bone density, wound healing, immune function, blood sugar regulation, and emotional well-being.^[9]

Smaller tumours that don’t produce hormones, called nonfunctioning microadenomas, often cause no detectable changes in the body. They’re too small to press on surrounding structures and they don’t alter hormone levels. This is why they’re frequently discovered only by accident during brain imaging performed for unrelated reasons. The body continues functioning normally despite their presence.^[2]