pituitary adenoma

pituitary adenoma
Name	Pituitary adenoma
Synonyms	Pituitary neuroendocrine tumor (PitNET)
Caption	Coronal MRI showing a pituitary macroadenoma
Field	Endocrinology, Neurosurgery
Symptoms	Variable, including headache, visual field loss, hormone excess or deficiency
Complications	Pituitary apoplexy, hypopituitarism, diabetes insipidus
Onset	Any age, peak 30–50
Duration	Chronic
Types	Functional (secreting) or non-functional; microadenoma or macroadenoma
Causes	Usually sporadic; rarely part of MEN1 or McCune-Albright syndrome
Risks	Family history of pituitary tumor syndromes
Diagnosis	Blood tests, MRI, visual field test
Treatment	Surgery (often transsphenoidal surgery), medication, radiation therapy
Prognosis	Generally good with treatment
Frequency	~15% of intracranial tumors

pituitary adenoma. A pituitary adenoma is a typically benign neoplasm arising from the pituitary gland at the base of the brain. These tumors are among the most common intracranial masses and can cause significant clinical issues through local mass effect or abnormal hormone secretion. While most are sporadic and non-cancerous, their location and endocrine activity necessitate careful management by specialists in endocrinology and neurosurgery.

Overview

Pituitary adenomas originate from the adenohypophysis within the sella turcica, a bony structure housing the pituitary gland. They represent a significant proportion of cases managed at major institutions like the Mayo Clinic and Massachusetts General Hospital. The clinical significance spans from incidental findings on MRI scans performed for other reasons to severe disorders driven by hormone excess, such as in Cushing's disease or acromegaly. Historical understanding of these tumors advanced significantly with the work of Harvey Cushing, a pioneer in the field of neurosurgery.

Classification and types

Adenomas are primarily classified by size and function. Microadenomas are less than 10 mm, while macroadenomas are 10 mm or larger, a distinction critical for treatment planning. Functional adenomas secrete hormones and are named for their cell of origin: prolactinomas (from lactotrophs), somatotroph adenomas (causing acromegaly), corticotroph adenomas (causing Cushing's disease), and others like thyrotroph adenomas and gonadotroph adenomas. Non-functional adenomas, which do not secrete active hormones, are often gonadotroph in origin. The World Health Organization classification also considers factors like Ki-67 proliferation index.

Signs and symptoms

Symptoms result from hormone hypersecretion, local mass effect, or pituitary gland dysfunction. Prolactinomas may cause galactorrhea and hypogonadism, while acromegaly presents with enlarged hands and feet. Cushing's disease leads to central obesity and hypertension. Mass effects from larger tumors commonly cause headache, bitemporal hemianopsia from optic chiasm compression, and cranial nerve palsies (e.g., oculomotor nerve). Hypopituitarism can cause fatigue, hypothyroidism, and adrenal insufficiency. Sudden worsening may indicate pituitary apoplexy.

Causes and risk factors

Most cases are sporadic with no clear cause, involving acquired mutations in pituitary cells. Recognized genetic syndromes significantly increase risk, including Multiple endocrine neoplasia type 1 (associated with MEN1 gene mutations), McCune-Albright syndrome (from GNAS gene mutations), and Familial isolated pituitary adenoma (often linked to the AIP gene). Other associated conditions include Carney complex and Succinate dehydrogenase-related familial syndromes. There are no consistent environmental or lifestyle risk factors identified.

Diagnosis

Diagnosis involves biochemical evaluation and imaging. Blood tests assess hormone levels: prolactin, insulin-like growth factor 1, cortisol, ACTH, TSH, FSH, LH, testosterone, and estradiol. Dynamic testing, like the oral glucose tolerance test for acromegaly or dexamethasone suppression test for Cushing's syndrome, is often required. MRI of the pituitary gland with contrast is the gold standard for visualizing the tumor and its relationship to the cavernous sinus and optic chiasm. A visual field test is crucial for tumors abutting the optic chiasm.

Treatment

Management is multidisciplinary. Surgery, typically via transsphenoidal surgery (often endoscopic), is first-line for most symptomatic non-prolactinomas and tumors causing mass effect. Medication is first-line for prolactinomas (dopamine agonists like cabergoline) and for acromegaly (somatostatin analogues like octreotide). Radiation therapy, including stereotactic radiosurgery (e.g., Gamma Knife), is used for residual or recurrent disease. Hormone replacement therapy (e.g., levothyroxine, hydrocortisone) is essential for managing hypopituitarism.

Prognosis and complications

Prognosis is generally favorable, especially for microadenomas and well-controlled prolactinomas. Cure rates for Cushing's disease and acromegaly via surgery vary. Potential complications include tumor recurrence, persistent hypopituitarism requiring lifelong replacement, and diabetes insipidus from damage to the posterior pituitary. Pituitary apoplexy is a neurosurgical emergency. Long-term follow-up at centers like the National Institutes of Health is standard to monitor for recurrence and manage endocrine function.

Category:Endocrine diseases Category:Neurological disorders