The pituitary is a gland about the size of a pea and is located towards the base of the brain. It is found behind the nose and the sphenoid sinus (air space behind the face), right below another important and related structure called the hypothalamus.
A gland is an organ that makes and releases hormones, that act on other organs and tissues to make them work. The pituitary is called the "master gland" because its hormones regulate the balance of hormones made by most of the other glands in the body. This way, the pituitary controls many processes, such as growth, development, and reproduction. It also controls the function of certain organs, such as the kidneys, breasts, and uterus.
The pituitary has three parts or lobes, each with its own job in the body. The front lobe, the anterior pituitary, makes up about 80% of the gland and is found closest to the front of the head. Its job is to make and release many "signalling" hormones into the bloodstream. These hormones move through the blood to other glands and organs, where they signal the organs and glands to start or stop working.
The intermediary lobe secretes only one hormone. This hormone affects skin pigmentation.
The back part of the gland, the posterior pituitary, does not make any hormones itself. Instead, it contains nerve endings of brain cells that come from the hypothalamus. These brain cells make the hormones, which then move down to and are stored in the posterior pituitary for later use.
The hypothalamus and the pituitary work hand-in-hand. The hypothalamus makes hormones that, in turn, signal the pituitary to release its hormones.
What is a pituitary adenoma?
A pituitary adenoma is a growth or tumour on the pituitary. Most pituitary adenomas are slow-growing and benign, which means they are not cancerous and do not spread to other parts of the body. However, as they grow big they can put pressure on nearby structures, such as the nerves that connect the eyes to the brain, and cause visual loss symptoms.
A large adenoma can also crush normal pituitary cells and keep them from working properly, leading to a reduction of hormone production (hypopituitarism). This condition can cause low blood pressure, tiredness, and changes in your sex drive and function. It can also make you feel less able to manage stress.
Pituitary adenomas are labelled based on their size. Tumours smaller than 1 cm are called microadenomas. Tumours bigger than 1 cm are called macroadenomas. Many adenomas cause symptoms by releasing extra hormones into the bloodstream and they are called functional adenomas.
Not all adenomas make hormones. Some, called non-functioning or null cell adenomas, do not make hormones. About one-third of all pituitary tumours are non-functioning adenomas. They usually become large and are found because they cause symptoms due to the mass effect.
How common are pituitary adenomas?
Pituitary adenomas make up 10% to 15% of all tumours that develop within the skull. They are found in about 77 out of 100,000 people, although it is believed that they actually occur in as many as 20% of people at some point in their lives. However, many pituitary adenomas, especially microadenomas, do not cause serious symptoms and are never found. Macroadenomas are about twice as common as microadenomas. Pituitary adenomas can occur at any age but are more common in people in their 30s or 40s. They are rarely found in those younger than 20. Women get adenomas more often than men.
What causes pituitary adenomas?
The exact cause of pituitary adenomas is not known. They have been linked to genetic mutations and most often happen on their own during a persons life.
What are the symptoms of a pituitary adenoma?
The symptoms of pituitary adenomas vary depending on the type of hormone released by the tumour or its mass effect on nearby structures. Having too many hormones can lead to certain disorders or syndromes, including:
- Gigantism in children and acromegaly in adults from too much growth hormone (GH)
- Cushing’s disease from too much adrenocorticotropic hormone (ACTH), which triggers the adrenal glands to make steroid hormones
- Hyperthyroidism from too much thyroid stimulating hormone (TSH)
Some general symptoms of pituitary adenomas include:
- Vision problems (double vision, vision loss)
- Sexual dysfunction
- Fatigue (extreme tiredness)
- Unexplained weight gain or loss
- Achy joints or muscle weakness
- Early menopause
- Changes in your monthly periods (women)
- Nausea or vomiting
- Changes in behaviour, including hostility, depression and anxiety
- Changes in the sense of smell
- Nasal drainage