Hypophyseal Adenoma: Classification, Types, Causes, Symptoms, Diagnosis, Treatment and Prevention

Also called pituitary tumor, it is a benign tumor (not cancerous) of the pituitary gland .

Most pituitary tumors are pituitary adenomas, slow-growing benign tumors that arise from the cells of the pituitary gland, which means they do not spread to distant parts of the body.

Incidence of pituitary adenomas

Pituitary adenomas are relatively common. Small microscopic pituitary adenomas are found in one in five adults. However, most of these tumors never grow or cause problems.

Often, a patient undergoes a magnetic resonance imaging (MRI) scan of the brain for another reason, and the doctor discovers a pituitary adenoma.

Pituitary gland

The pituitary gland is located at the base of the brain, just behind the eyes.

The pituitary gland has different types of pituitary cells , each one producing special hormones released into the bloodstream that affect other organs in the body.

Pituitary tumors originate from one of these specialized cells. If the tumor cells produce an excess of one or more hormones, it is called a “functional” adenoma. Examples of functional adenomas include:

  • Prolactinoma, a tumor that produces excess prolactin.
  • Gigantism (infantile) due to acromegaly (adults), caused by an excess of growth hormone.
  • Cushing’s disease, caused by a pituitary tumor that stimulates an excessive production of cortisol.

Classification of pituitary adenomas

Pituitary adenomas are classified in different ways according to their properties:

  • Size:  a microadenoma is less than one centimeter in size; A macroadenoma is one centimeter or more in size.
  • Aggressiveness: almost all pituitary adenomas are benign (non-cancerous) and slow-growing. An atypical pituitary adenoma, the rarest type, grows more quickly and is more likely to reappear.
  • Hormone secretion: pituitary adenomas that release an active hormone (usually an excessive amount) are called functional tumors. If they do not release an active hormone, they are called adenomas that do not work clinically.

Types of pituitary adenomas

  • Functional pituitary adenomas:  excess secrete one or more hormones such as prolactin, growth hormone, adrenocorticotropic hormone, thyroid stimulating hormone, luteinizing hormone and follicle stimulating hormone.
  • Non-functional pituitary adenomas: do not secrete hormones.
  • Macroadenomas: they are large (more than 1 centimeter) and can compress adjacent structures, causing serious complications, such as loss of vision. They also affect the function of the pituitary and cause hormone deficiencies.
  • Microadenomas: they are small (less than 1 centimeter) and rarely compress nearby tissues, but can be harmful if they secrete excessive hormones.

Causes

Most pituitary adenomas occur spontaneously, which means they are not inherited.

There are cases of familial pituitary tumors, which is a hereditary tendency to develop pituitary adenomas. However, these cases are rare. In many familial cases, gigantism or the early onset of acromegaly are more common.

Multiple endocrine neoplasia type 1 (MEN 1) is a rare entity characterized by simultaneous tumors of the pituitary, pancreas, and parathyroid glands. Pituitary adenomas develop in 25 percent of patients with MEN 1.

symptom

The symptoms produced by pituitary adenomas depend on several factors, even if the tumors produce hormones or clinically do not work.

  • Functional pituitary adenomas release an active hormone in excessive amounts into the bloodstream. Patients generally experience symptoms related to the action of the hormone in the body.
  • Nonfunctioning pituitary adenomas usually cause problems related to the size of the tumor, which pushes the surrounding brain structures.
  • Large pituitary tumors can compress the optic chiasm , the crossing point of the optic nerves, leading to vision loss. They can also compress the normal pituitary gland and cause pituitary insufficiency.

Hormone-producing pituitary tumors can also grow in large sizes, causing the same problems described above in addition to the effects related to hormones.

Symptoms related to the effect of a macroadenoma

  • Vision loss: this occurs when the macroadenomas grow up into the brain cavity, compressing the optic chiasm.
  • Bitemporal hemianopsia :  a loss of external peripheral vision. When it is severe, a patient can only see what is directly in front of them.

Symptoms related to pituitary insufficiency

When the tumor compresses the normal pituitary gland, it can cause it to fail and lead to pituitary insufficiency ( hypopituitarism ). The symptoms will depend on which hormone is involved.

  • Reduction of sex hormones, luteinizing hormone (LH) and follicle-stimulating hormone.
  • The reduction in the production of thyrotropinoma can cause hypothyroidism , which can cause loss of appetite, weight gain, fatigue and decreased mental function.
  • The reduction in the production of growth hormone is called growth hormone insufficiency.
  • The reduction in prolactin production is uncommon and occurs with severe pituitary insufficiency.
  • Large pituitary tumors can slightly elevate prolactin levels in the blood.
  • Headache.

Diagnosis

A pituitary adenoma may be suspected based on symptoms, medical history, and physical findings.

Explaining your symptoms is a crucial part of the diagnosis, since your doctor uses the information to determine if a pituitary tumor is secreting an excess of hormones and if there is evidence of pituitary insufficiency.

Standard diagnostic tests include:

  • Hormonal tests
  • Pituitary function tests for patients with pituitary tumor.
  • Image scans.

Treatment

The treatment of a pituitary adenoma depends on several factors, including:

  • Hormone production by the tumor (if present).
  • Tumor size
  • The extent to which the tumor invaded the surrounding structures.
  • Your age and general health.

If you have a hormone-producing pituitary adenoma, it can sometimes be treated medically. An endocrinologist who specializes in hormone-producing tumors, called a neuroendocrinologist, may be needed to manage your care.

The medication can help certain pituitary tumors. Prolactinomas are often treated only with medications and may not require surgery.

The medication plays an important role in the management of Cushing’s disease and acromegaly.

It is also important to address pituitary insufficiency ( hypopituitarism ), especially before surgery. Inadequate cortisol or thyroid levels can be life-threatening if not treated before surgery.

If pituitary adenomas require surgery, generally the best procedure is through a nasal approach. This procedure eliminates the tumor and minimizes complications, hospitalization time and discomfort.

Very large tumors that extend into the cavity of the brain may require the opening of the skull ( craniotomy ) to access the tumor.

Some tumors can not be removed surgically and may not respond to medications. Radiation therapy can be effective in controlling the growth of these tumors.

One consequence of radiation treatment is that it can cause a delay in the failure of the pituitary gland. This usually happens several years after the treatment. If this happens, it will require hormone replacement.

Prevention

Pituitary adenomas are not associated with any known lifestyle or environmental risk factors, so there are no methods available to prevent the condition.

People with a family history of pituitary tumors associated with hereditary genetic syndromes should be monitored regularly for early signs of the disorder.