Pituitary adenoma

Epidemiology

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Etiology

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Pathophysiology

• Tumor classification according to ability to secrete hormones
  • Nonsecretory pituitary adenomas
    • Nonfunctioning tumors account for 15–45% of all pituitary adenomas.
    • Gonadotroph adenomas
    • Null cell adenomas
    • Plurihormonal adenomas
    • Silent somatotroph and corticotroph adenomas
  • Secretory pituitary adenomas: hormone secretion → hyperpituitarism
    • Most exclusively proliferate in only one type of endocrine cell and therefore secrete only one pituitary hormone.

Tip

Prolactinomas are the most common pituitary adenomas.

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Clinical features

• Mass Effect (especially Macroadenomas >1 cm):
  • Headaches are a common symptom.
  • Bitemporal hemianopsia: Classic visual field defect due to compression of the optic chiasm.
  • Cranial nerve palsies from invasion of the cavernous sinus (CN III, IV, V1, V2, VI).
  • Hypopituitarism: Compression of normal pituitary tissue leading to hormone deficiencies (e.g., hypothyroidism, hypogonadism).
• Hormone Hypersecretion (Functional Adenomas):
  • Prolactinoma (Most common type, ~40%):
    • See Hyperprolactinemia
  • Somatotroph (GH-secreting) Adenoma:
    • Acromegaly (Adults): Coarsening of facial features, large hands/feet, frontal bossing, prognathism, glucose intolerance/DM, HTN.
    • Gigantism (Children/Adolescents with open epiphyseal plates): Increased linear growth.
  • Corticotroph (ACTH-secreting) Adenoma (Cushing Disease):
    • Causes about 70% of endogenous Cushing’s syndrome.
    • Features: Central obesity, moon facies, buffalo hump, purple striae, proximal muscle weakness, HTN, hyperglycemia, osteoporosis.

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Diagnostics

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Treatment

• Prolactinoma:
  • Dopamine agonists (e.g., Cabergoline, Bromocriptine) are first-line therapy. They decrease prolactin levels and shrink the tumor.
  • Transsphenoidal surgery is reserved for patients who do not respond to or cannot tolerate medical therapy.
• Acromegaly & Cushing’s Disease:
  • Transsphenoidal surgery is the primary treatment.
  • Medical therapy can be used adjunctively. For acromegaly, options include somatostatin analogs (e.g., Octreotide) or GH receptor antagonists (e.g., Pegvisomant). For Cushing’s, adrenal enzyme inhibitors (e.g., Ketoconazole) can be used.
  • Radiation therapy may be used for residual or recurrent tumors.
• Non-functioning Adenoma:
  • Observation for small, asymptomatic tumors.
  • Transsphenoidal surgery if mass effect symptoms (e.g., vision changes) are present.

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