Skip to content

Pituitary Adenoma

BASICS

  • Definition: Benign, slow-growing tumor of the pituitary gland; may secrete hormones or cause mass effects.
  • Subtypes (hormonal):
  • Prolactinoma (PRL): 25–40%
  • Nonfunctioning: 30%
  • Somatotroph (GH): 15–20%
  • Corticotroph (ACTH): 5–10%
  • Thyrotroph (TSH): <1%
  • Gonadotroph (LH/FSH), Mixed
  • Microadenoma: <10 mm; Macroadenoma: ≥10 mm

EPIDEMIOLOGY

  • Prevalence (autopsy): Microadenomas 3–27%, Macroadenomas <0.5%
  • Clinically apparent: 18/100,000 people

ETIOLOGY & PATHOPHYSIOLOGY

  • Origin: Monoclonal adenohypophysial cell growth
  • Diagnosis often prompted by:
  • Hormonal effects (functional microadenoma)
  • Mass effect (visual field deficits, headache)
  • Genetic associations:
  • 15% have AIP gene mutation (familial isolated pituitary adenoma); tend to be younger and larger tumors

RISK FACTORS

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

DIAGNOSIS

History

  • Hyperprolactinemia: infertility, amenorrhea, galactorrhea, gynecomastia, impotence
  • Mass effect: headache, bitemporal hemianopsia (visual field loss)
  • Acromegaly (GH excess): coarse features, hand/foot swelling, carpal tunnel, LVH
  • Cushing disease (ACTH excess): moon face, truncal obesity, striae, hirsutism
  • Apoplexy: sudden headache/collapse (rare, life-threatening)
  • Secondary hormone deficiencies: FTT in children, hypogonadism, secondary hypothyroidism or adrenal insufficiency

Physical Exam

  • Visual deficits: bitemporal hemianopsia
  • Acromegaly: coarse features, diaphoresis
  • Cushingoid features: central obesity, fat pad, striae, hirsutism
  • Hypopituitarism: failure to thrive, hypotension, hypoglycemia

Differential Diagnosis

  • Pituitary hyperplasia (e.g., pregnancy, hypothyroidism), Rathke cleft cyst, craniopharyngioma, metastatic tumor, lymphocytic hypophysitis, granulomatous disease

Diagnostic Testing

  • Hormonal Panel:
  • PRL, GH, IGF-1, ACTH, 24-hr urinary-free cortisol, overnight DMST, β-HCG, FSH, LH, TSH, free T4
  • Imaging: MRI is gold standard (>90% sensitivity/specificity)
  • Specialized testing: Octreotide scan (somatostatin receptor), oral glucose suppression test for acromegaly, macimorelin test for adult GH deficiency

Lab Patterns by Subtype

  • Prolactinoma: PRL >20 ng/mL
  • Acromegaly: ↑IGF-1, failure of GH suppression on glucose test
  • Cushing disease: ↑24h urinary cortisol, abnormal DMST, ACTH level
  • TSH-oma: Both TSH & free T4 ↑ (central hyperthyroidism)
  • Nonfunctioning: usually mass effect

TREATMENT

Medical Therapy (First Line)

  • Prolactinoma: Dopamine agonists
  • Cabergoline: 0.25 mg 1–2x/week, titrate per PRL
  • Bromocriptine: 1.25–2.5 mg PO daily, titrate as needed
  • Somatotroph (GH): Somatostatin analogs (octreotide, lanreotide), pegvisomant (GH receptor antagonist)
  • Corticotroph (ACTH): Mitotane, ketoconazole, pasireotide, mifepristone
  • Second line: Metyrapone, octreotide (gonadotropinoma, thyrotropinoma)

Surgical Therapy

  • Indications: Symptomatic macroadenomas (mass effect, vision loss), non-PRL tumors
  • Approach: Endoscopic transsphenoidal resection is preferred

Adjunct Therapy

  • Radiotherapy: Fractionated or stereotactic (for residual or recurrent tumor)
  • Medical adjunct: Used if surgery incomplete/contraindicated or as adjuvant to reduce recurrence

Referral

  • Neurosurgery for symptomatic macroadenoma (except PRL, usually medical first)
  • Endocrinology for hormonal evaluation and long-term follow-up

ONGOING CARE

  • Imaging: MRI at 6 and 12 months post-surgery, then per clinical judgment
  • Hormonal labs: Monitor involved hormone(s) post-op; hypopituitarism may develop 10–15 years after radiotherapy

PROGNOSIS

  • Depends on: Subtype, size, response to therapy, surgical success
  • Complications:
  • Post-op: transient diabetes insipidus, hypogonadism
  • Apoplexy (acute hemorrhagic infarction): surgical emergency
  • Nelson syndrome (post-adrenalectomy rapid tumor growth)
  • Chronic: pituitary hormone insufficiency, optic neuropathy (after >60 Gy radiation)

ICD-10

  • D35.2 Benign neoplasm of pituitary gland

CLINICAL PEARLS

  • Incidentaloma: Asymptomatic microadenoma on imaging; screen for PRL, GH/IGF-1, ACTH/cortisol, FSH, LH, TSH, free T4
  • Initial therapy: Dopamine agonist for PRLs, surgery for others
  • Pituitary apoplexy: Sudden hemorrhagic infarction—fatal without decompression