Pituitary adenoma is a special tumor with two major characteristics and three major treatments!

Author: Yu Shuqing, Chief Physician, Beijing Tiantan Hospital, Capital Medical University

Reviewer: Li Jingjing, Chief Physician, Beijing Tiantan Hospital, Capital Medical University

The pituitary gland is located in the middle of the brain. It is a very small organ, weighing only about 0.6 grams, but it is very important. Almost all the hormones needed by the human body are secreted by the pituitary gland.

Figure 1 Original copyright image, no permission to reprint

The pituitary gland is mainly divided into the adenohypophysis and the neurohypophysis. Tumors originating from the adenohypophysis are called pituitary adenomas, and the vast majority of pituitary adenomas are benign; tumors originating from the neurohypophysis are rare.

The pituitary gland contains many cells, including cells that secrete growth hormone, cells that secrete prolactin, cells that secrete adrenocorticotropic hormone, cells that secrete thyroid-stimulating hormone, etc. Gene mutations or other changes in these cells may induce the occurrence of pituitary adenomas, which is the main cause of the disease.

1. Pituitary adenoma has two major characteristics!

Pituitary adenoma originates from endocrine organs and is the only tumor in the brain that originates from endocrine organs, so it has its own particularity. The particularity is manifested in two aspects: one is the endocrine characteristics, and the other is the compression characteristics caused by the tumor.

Pituitary adenomas are divided into functional adenomas and non-functional adenomas according to whether they have endocrine function. According to the size of the tumor, those with a diameter of less than one centimeter are called microadenomas, and those with a diameter of more than one centimeter are called macroadenomas.

In addition to the characteristics of tumor compression, functional adenomas also have endocrine functions and can secrete various hormones. They are divided into growth hormone adenomas, prolactin adenomas, adrenocorticotropic hormone adenomas, thyroid stimulating hormone adenomas, follicle stimulating hormone/luteinizing hormone adenomas and other types.

Non-functional adenomas are somewhat similar to other tumors in the brain, such as gliomas and meningiomas. They have no endocrine function, but they have a space-occupying effect and can compress important surrounding nerves, blood vessels, and tissues, leading to corresponding symptoms.

2. What are the common symptoms or manifestations of pituitary adenoma?

The clinical symptoms of pituitary adenomas are related to hormone levels, tumor size, and degree of invasiveness.

One type of pituitary adenoma is a prolactin adenoma, which secretes prolactin and causes an increase in prolactin. The most common symptoms in female patients are amenorrhea, irregular menstruation, and amenorrhea with galactorrhea. If it is a growth hormone-producing pituitary adenoma, adolescents will be very tall, abnormally tall compared to their peers; adults will show acromegaly, such as an enlarged nose, larger fingers, and larger feet.

The pituitary gland is located in the center of the brain, behind the optic nerve. If the pituitary gland function is affected, the hormones needed by the human body will be secreted less, and the mental state may be bad. When the tumor grows, it will compress the optic nerve, causing blurred vision or narrowing of the field of vision; when the tumor grows backward, it will compress the hypothalamus and affect the function of the hypothalamus; when the tumor grows upward, it may compress the third ventricle, causing obstruction of the cerebrospinal fluid circulation pathway, leading to hydrocephalus, headache, nausea, decreased vision and other symptoms.

If symptoms appear and a problem with the pituitary gland is suspected, further blood tests are needed to check the levels of various hormones. If the level of a certain hormone is elevated, the next step may be an imaging test, such as CT or MRI, to detect lesions in the sellar region. Based on the clinical manifestations, it can be confirmed that it is a pituitary adenoma.

Even if a non-functional pituitary adenoma is larger than one centimeter, but it is completely within the sella turcica, does not compress the surrounding optic nerve or other tissues, and does not cause corresponding symptoms, it can be followed up regularly for observation. For symptomatic pituitary adenomas, listen to the advice of specialists based on the specific situation to see if treatment is needed and what treatment method is appropriate.

3. How to choose the treatment method for pituitary adenoma?

There are three main types of treatments for pituitary adenomas: surgery, medication, and gamma knife.

In terms of classification, if it is a growth hormone-producing pituitary adenoma, which grows particularly high or has acromegaly, surgery is the first choice to achieve the purpose of cure. If drug treatment for prolactin adenoma is ineffective or the effect is not obvious, surgical treatment is also required.

There are two main surgical methods: one is the transnasal sphenoidal approach, and the other is a craniotomy, called the transfrontal approach. The surgical method is determined by the location and pattern of tumor growth. If the pituitary gland grows in the sella turcica, just behind the nostrils, and the tumor is relatively small, it can be operated on through the nostrils, which is called the minimally invasive transnasal sphenoidal approach; if the tumor is relatively large and grows above or beside the sella turcica, a craniotomy is required.

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Prolactinomas, especially high prolactin adenomas, are treated with drugs to lower prolactin levels. Drugs are only useful for prolactin adenomas, not other types of pituitary adenomas.

Another treatment method is gamma knife radiotherapy. Gamma rays cause radiation to the human body, but the amount of radiation is acceptable. This treatment method was more popular several years ago because it is non-invasive. As of 2019, the gamma knife has limited therapeutic effect on pituitary adenomas. After gamma knife treatment, the tumor is still growing, and it is more difficult to perform surgery again, because the tumor hardens after radiation exposure and is severely adhered to the surrounding area, making it difficult to separate surgically. Therefore, gamma knife treatment is being performed less and less.

The recurrence rate of pituitary adenomas is relatively high. If they recur, they will grow faster and can be treated with a second surgery. If the tumor is still growing after surgery, gamma rays can be used to inhibit it, reduce its growth activity, and stop it from growing.