What are pituitary tumors?
Excessive growth of pituitary gland cells causes irregular growth, forming a pituitary tumor, also known as a pituitary adenoma.
This gland is considered the body’s main gland. Located at the base of the brain, the pituitary regulates the work of other glands, such as the adrenal, thyroid, testes, and ovaries. It also produces the hormones prolactin (essential for breastfeeding), oxytocin (important in labor), growth hormone, and secretes antidiuretic hormone, which helps control the body’s water balance.
Pituitary tumors are typically non-cancerous pituitary adenomas. However, despite being non-cancerous, they can cause significant health problems by either secreting hormones excessively or interrupting hormone production.
It is a rare disease, with tumors often being small and never causing any symptoms. It can occur at any age but is more common in older people.
The causes of pituitary tumor development are unknown.
Subtypes of pituitary tumors
Pituitary adenomas are classified based on two parameters: size and hormone production capacity.
Regarding size, pituitary adenomas can be:
- Microadenomas – tumors less than 1 cm in diameter, which rarely compromise or damage the pituitary site where they are located or the tissues near the gland. They only cause symptoms if they release some hormone in excess, but many people with microadenomas never diagnose them or suffer any health consequences from them; and
- Macroadenomas – tumors larger than 1 cm in diameter, which can cause symptoms due to excessive production of some hormone and/or by pressing on the normal pituitary tissue or nearby nerves, such as the optic nerve.
Regarding hormone production capacity, pituitary adenomas can be:
- Functional – these are pituitary adenomas that produce hormones in excess, classified according to the hormone they produce (prolactin – 30% to 40%; growth hormone – 20%; other types, such as corticotropin, gonadotropin, and thyrotropin). Some functional adenomas secrete more than one type of hormone; and
- Non-functional – also called null cell adenomas, these are pituitary adenomas that do not produce any type of hormone. They account for about 30% of pituitary tumors.
Very rarely, pituitary tumors can be malignant, and they are then called pituitary carcinomas. They can occur at any age but are more common in older individuals, and they usually produce hormones.
Symptoms of pituitary tumors
The symptoms of pituitary tumors depend on the type of hormone produced in excess or not produced due to the disease. In general, different types of tumors in this gland cause headaches, weakness, joint pain, and unexplained weight loss or gain.
Pituitary tumors can cause specific symptoms, such as gigantism before puberty or acromegaly after puberty (when there is excessive production of growth hormone), diabetes insipidus (if there is less release of vasopressin due to compression of the hypothalamus), amenorrhea in women and erectile dysfunction in men (excessive production of prolactin), and Cushing’s syndrome (excessive production of ACTH).
Diagnosis of pituitary tumor
The suspicion of a pituitary tumor arises when the patient presents with unexplained headaches along with other symptoms, but in many cases these tumors are discovered incidentally, in exams performed due to another disease.
As benign adenomas usually cause hormonal changes, specific blood and urine tests are performed to evaluate their levels. Then, imaging tests such as computed tomography and magnetic resonance imaging are done to verify if the pituitary tumor affects other nearby structures. In most of these cases, a biopsy of a small sample of tissue from the affected area is the test that confirms the diagnosis.
Pituitary carcinomas are very similar to adenomas in the region, so they are usually diagnosed when they spread to other organs. This typically occurs 5 to 10 years after the initial surgery to treat the issue. The sites to which these malignant tumors tend to spread are the brain, spinal cord, meninges, or bone around the pituitary gland.
Treatment for pituitary tumors
Pituitary tumors can be treated with medications, surgery, or a combination of both, depending on the case and the evaluation of the specialist.
Generally, pituitary tumors that secrete ACTH, growth hormone, or TSH are surgically removed; when they are inaccessible or multifocal, radiation therapy is necessary. Prolactin-producing adenomas, on the other hand, can be treated with medications, making surgery and radiation therapy unnecessary.
After treatment, monitoring of pituitary gland hormone levels should be performed; if they do not normalize, medication may be necessary.
Prevention of pituitary tumors
Since pituitary tumors have no known cause, it is not possible to prevent them.
