Pituitary adenoma overview

# Overview
Pituitary adenomas are tumors that occur in the pituitary gland and account for about 10% of intracranial neoplasms. Pituitary adenomas are often remain undiagnosed. Small pituitary adenoms are found in 6 to 24 percent of adults at autopsy.
Pituitary adenomas arise within the anterior lobe (adenohypophysis) of the gland. Pituitary adenomas may be classified according to the size of the adenoma and type of hormone secretion. Pituitary adenomas subtypes include corticotrophic, somatotrophic, thyrotrophic, gonadotrophic, and lactrotrophic adenomas. Adenomas less than 10mm are called microadenomas. There are no established causes for pituitary adenoma. Patients with pituitary adenoma may progress to develop lethargy, headache, nausea, and vomiting. Common complications of pituitary adenoma include bitemporal hemianopia, anosmia, acromegaly, gigantism, and Cushing's syndrome.
Prognosis is generally good, and approximately 18% of patients with macroadenoma require further treatment. Pharmacologic medical therapy is recommended among patients with prolactinoma, thyrotrophic, somatotrophic, and adrenocorticotropic adenomas.
The transsphenoidal microsurgical approach is the mainstay of treatment for growth hormone-(GH) producing adenomas, adrenocorticotropic hormone-(ACTH) producing adenomas, and macroadenomas.

# Historical Perspective
Pituitary adenoma was first described by Pierre Marie, a French neurologist in 1886.

# Classification
Congenital adrenal hyperplasia due to 21-hydroxylase deficiency may be classified into several subtypes based on severity, time of onset (mild, moderate, and severe), and the presence of virilization (stage I to stage V).

# Pathophysiology
On gross pathology, a well circumscribed suprasellar mass is a characteristic finding of pituitary adenoma.
On microscopic histopathological analysis, a monomorphic expansion of usually one cell type with lack of reticulin network among neoplastic cells is a characteristic finding of pituitary adenoma.

# Causes
There are no established causes for pituitary adenoma.

# Differential Diagnosis
Pituitary adenoma must be differentiated from other diseases such as craniopharyngioma, meningioma, arachnoid cyst, and pituitary carcinoma.

# Epidemiology and Demographics
The prevalence of pituitary adenoma is approximately 100 per 100,000 individuals worldwide. In the USA, the incidence pituitary adenoma is approximately 3.12 per 100,000 individuals.

# Risk Factors
The most potent risk factor in the development of pituitary adenoma is a positive family history of either pituitary tumor, multiple endocrine neoplasia type 1 (MEN1), or McCune-Albright syndrome.

# Pituitary adenoma natural history, complications, and prognosis
Patients with pituitary adenoma may progress to develop lethargy, headache, nausea, and vomiting. Common complications of pituitary adenoma include bitemporal hemianopia , anosmia, acromegaly, gigantism, and Cushing's syndrome.
Prognosis is generally good, and approximately 18% of patients with macroadenoma require further treatment.

# Diagnosis

## Staging
According to the American Joint Committee on Cancer classification and staging system for pituitary tumors, there is no staging system available for pituitary adenoma.

## History and Symptoms
The hallmark of pituitary adenoma is increased intracranial pressure. A positive history of visual field defect, headache, and menstrual irregularities is suggestive of pituitary adenoma. The most common symptoms of pituitary adenoma include  galactorrhea, oligomenorrhea , erectile dysfunction, and loss of libido.

## Physical Examination
The presence of altered mental status, nausea, lethargy, and visual filed defect (bitemporal hemianopsia) on physical examination is suggestive of pituitary adenoma.

## Laboratory Findings
Laboratory findings consistent with the diagnosis of pituitary adenoma include elevated serum prolactin level and elevated or decreased serum levels of other pituitary hormones.

## CT
On head CT scan may be helpful in the diagnosis of pituitary adenoma. Findings on CT scan suggestive of pituitary adenoma include a large suprasellar mass that invades surrounding structures, calcification, and rarely hemorrhage.

## MRI
On brain MRI, pituitary adenoma is characterized by a large mass with heterogeneous signal. Other findings may include remodeling of the floor of the sella and deviation of the pituitary infundibulum to the opposite side.

## Other Imaging Studies
Historically, before the advent of MRI, lateral skull x-rays were performed to look for remodelling of the pituitary fossa.

## Other Diagnostic Studies
Inferior petrosal sinus sampling may be performed to detect hormonally active pituitary microadenoma.

# Treatment

## Medical Therapy
Pharmacologic medical therapy is recommended among patients with prolactinoma, thyrotrophic, somatotrophic, and adrenocorticotropic adenomas.

## Surgery
The transsphenoidal  microsurgical approach is the mainstay of treatment for growth hormone-(GH) producing adenomas, adrenocorticotropic hormone-(ACTH) producing adenomas, and macroadenomas.

## Primary Prevention
There are no primary preventive measures available for pituitary adenoma.

## Secondary Prevention
Secondary prevention strategies following pituitary adenoma include a regular check up of pituitary hormones serum levels and regular neuro-ophthalmic examination.