Pituitary Adenoma

Description

Typically benign, slow-growing tumors that arise from cells in the pituitary gland

• Presenting symptoms include neurologic deficits, visual changes including diplopia, and headaches.
• Subtypes (hormonal): prolactinoma (PRL) 25–40%, nonfunctioning pituitary adenomas 30%, somatotroph adenoma (growth hormone [GH]) 15–20%, corticotroph adenoma (adrenocorticotropic hormone [ACTH]) 5–10%, thyrotroph adenoma (thyroid-stimulating hormone [TSH]) <1%, gonadotropinoma (luteinizing hormone/follicle-stimulating hormone [LH/FSH]), mixed (1)[A]
• Defined as microadenoma <10 mm and macroadenoma ≥10 mm
• May secrete hormones and/or cause mass effects or visual changes

Epidemiology

Incidence

• Autopsy studies have found microadenomas in 3–27% and macroadenomas in <0.5% of people without any pituitary disorders.
• Clinically apparent pituitary tumors are seen in 18/100,000 persons.

Etiology and Pathophysiology

• Monoclonal adenohypophysial cell growth
• Hormonal effects of functional microadenomas often prompt diagnosis before mass effect.
• PRL increased by functional PRLs or inhibited dopaminergic suppression by stalk effect

Genetics
Familial isolated pituitary adenomas: ~15% have mutations in the aryl hydrocarbon receptor–interacting protein gene (AIP); present at a younger age and are larger in size (2)

Risk Factors

Multiple endocrine neoplasias

Commonly Associated Conditions

• McCune-Albright syndrome
• Multiple endocrine neoplasia type 1 (MEN1)