Pituitary adenomas are non-cancerous adenomas (tumors) which appear on the pituitary gland (a gland which secretes several hormones and helps in regulating various other important glands) in the sellar region of the brain. The adenomas which are greater than 10 millimeters in size are classified as macroadenoma and those smaller than 10 millimeters are known as microadenomas. These benign tumors can lead to vision problems as they are close to the eyes and growth problems by disrupting thyroid functions.
Epidemiology
A study published in the National Center for Biotechnology Information on their online portal gave a systematic review of pituitary macroadenoma prevalence. The study conducted by Ezzat S, Cloudwell WT and colleagues from University of Toronto and Mount Sinai Hospital, found an overall estimated prevalence of pituitary adenomas of 16.7% (14.4% in autopsy studies and 22.5% in radiological studies.).
In the United States, pituitary adenomas are found in as many as 25% cases on autopsy of unselected cases as detection of these neoplasms is mostly by chance. There is no specific race or ethnic community that is affected by this disease. Though these tumors affect individuals of every age, there has been an increase in incidence amongst individuals in their 30s and 60s. The corticotrominomas (a type of pituitary adenoma) is observed mainly in women with the female to male ratio standing at 4:1.
Types of Adenomas
Pituitary adenomas are classified with respect to their growth, anatomy, functions and histology.
- Size
Based on size, there are two types of Adenomas; those less than 10 mm in size are called microadenomas and those more than 10 mm in size are called as macroadenomas. The radioanatomical findings give a more diverse classification by placing adenomas into 4 grades:
1. Grade I: microadenomas without sella expansion
2. Grade II: macroadenomas and may extend above the sella
3. Grade III: macroadenomas with suprasellar expansion
4. Grade IV: destruction of the sella
- Histology
The histological classification depends on the hormone secreted by the adenoma. Approximately 20-25% tumors do not secrete any kind of identifiable active hormones. These are called non-functioning tumors.
- Function
The functional classification of adenomas is based upon the adenomas’ endocrine activity determined by serum hormone levels detected through immunohistochemical staining.
- Growth
Almost all of pituitary macroadenomas are benign (non-cancerous) and characterized by slow growth. An atypical pituitary adenoma like pituitary carcinomas, grows at a rapid pace and has recurring tendencies.
Pituitary Macroadenoma Symptoms
The symptoms displayed by patients suffering from pituitary adenoma can be physical and psychiatric both.
- Symptoms related to over production of hormones
There can be distinguishable symptoms displayed by patients suffering from over production of hormones related to that specific hormone.
1. Prolactinoma
Overproduction of prolactin causes loss of menstrual periods and breast milk production in women. Excessive production of prolactin in men can lower the levels of testosterone, causing lack of sexual interest and erectile dysfunction.
2. Growth Hormone (GH) secreting adenoma
The excessive production of the growth hormone leads to acromegaly in adults and gigantism in children. The detection of physical abnormality in adults is easy as compared to children. It is characterized by enlargement of hands and feet, as well as other abnormalities in the body.
3. ACTH-secreting pituitary adenoma
Surplus production of ACTH leads to Cushing’s disease which is characterized by weight gain, easy bruising of skin and muscle weakness.
- Symptoms related to visual problems
Macroadenomas that grow uncontrollably into the brain cavity may cause visual field defects known as the bitemporal hemianopia. The tumor growing upward causes compression of the optic nerve in the optic chiasma region.
- Symptoms related to pituitary insufficiency
Hypopituitarism is caused when the tumor grows and suppresses the normal functioning of pituitary gland. The symptoms displayed during this condition depend on the hormone involved:
- Reduction in sex hormones, luteinizing hormones and follicle- stimulating hormones can lead to lack of sexual interest and erectile dysfunction in men and infertility in women.
- Reduction in TSH production leads to hypothyroidism which can cause appetite loss, weight gain, fatigue and reduced mental functioning.
- Below normal production of GH results in stunted growth of low puberty in children, whereas leads to tiredness, loss of muscle mass and tone in adults.
- Reduction in ACTH production will result into fatigue, low blood pressure and electrolyte abnormalities.
- Other physical symptoms observed are various types of headaches like episodic migraines, chronic migraines, unilateral headaches, primary stabbing headaches, cluster headache and hemicrania continua.
Causes
The exact cause of pituatory macroadenoma is yet unknown. The most widely accepted theory of occurrence of pituitary adenoma is spontaneous occurrence. There have been cases where these tumors are related to other endocrine disorders associated with genetic changes. Multiple Endocrine Neoplasia type 1 (MEN 1) is causes pituitary adenomas as a part of its simultaneous tumor growth.
Diagnosis
Diagnosis of pituitary adenoma is mostly incident diagnosis which is a chance discovery while performing an evaluation of unrelated medical conditions. The most popular diagnosis methods are:
- Physical test
In case of bitemporal hemianopia, a visual field test might be recommended to test for blurry vision and visual field defects.
- Hormone tests
Hormone testing is done to detect functional adenoma and pituitary insufficiency. The differential diagnosis is supplemented by dynamic hormone tests to determine the exact hormone defect. Treatment of some functional tumors can be done without surgery and hence comprehensive testing is necessary to calculate the severity of the tumor.
- Imaging tests
Computed Tomography (CT) scanning is better at depicting bony structure and calcifications within soft tissues. A CT scan might be recommended for differential diagnosis of tumors.
Magnetic Resonance Imaging (MRI) scans might be used for more detailed imaging of tissues and vascular organs. A 3T MRI scanner will give detailed images of a tumor which are not visible to normal MRI scanners.
Treatment
There are various treatment options available for pituitary macroadenoma like surgery, medication, radiation therapy and radio surgery. The specific treatment of adenoma is coordinated between a neurosurgeon and endocrinologist.
Surgery
The first line of treatment for pituitary macroadenoma is surgery. A transsphenoidal approach is undertaken by surgeons to reach beyond your sphenoid bone (the bone behind your nose) to reach the pituitary gland. With the help of surgical instruments an incision is made through the nasal cavity to reach the sella trucica (the bone that protects pituitary gland). Once a hole is made in the sella trucica, with the help of high magnification, tumor is distinguished from the gland. The tumor is removed and the cavity cleaned and sealed.
Medication
For fluctuating hormone levels in the body caused by dysfunction of the pituatory gland, medication may be prescribed by the medical practitioner. The medication provided either replaces the natural hormones with synthetic hormones or stymies the action of macroadenoma on the pituitary gland.
Radiosurgery
Gamma knife surgery is the most commonly used form of radiotherapy which replaces traditional surgery practice. The knife here is made up of several gamma rays which are not harmful individually but when converged and concentrated on a single point, prove lethal for the tumor. Radio therapy is a long process and result might take years to show, as compared to the comparatively quick results of traditional therapy.
