Acromegaly
Acromegaly is a hormonal disorder caused by a pituitary tumor producing too much growth hormone, leading to enlarged hands, feet, and facial features.
Emergency Management: Pituitary apoplexy: a life-threatening hemorrhage into the adenoma, causing sudden headache, visual loss, ophthalmoplegia, and acute adrenal insufficiency. Requires immediate high-dose IV hydrocortisone (100 mg) and urgent neurosurgical decompression.
A rare, insidious endocrine disorder caused by the excessive secretion of growth hormone (GH), almost exclusively from a benign pituitary adenoma. The chronic GH excess leads to elevated insulin-like growth factor 1 (IGF-1), resulting in overgrowth of bone, cartilage, and soft tissues, primarily affecting the extremities and face after the epiphyseal plates have fused.
Detailed Overview
Acromegaly develops slowly over decades. The persistent elevation of GH and IGF-1 induces somatic hypertrophy, metabolic dysfunction (insulin resistance, diabetes mellitus), and cardiovascular disease (cardiomyopathy, hypertension). Because the growth plates are closed, patients do not grow taller (unlike gigantism in children), but instead experience acral enlargement (hands, feet, jaw). Cardiovascular and respiratory complications are the leading causes of premature mortality if untreated. Early diagnosis is often missed due to the insidious phenotypic changes.
Epidemiology & Demographics
Incidence: 3-4 cases per million person-years. Prevalence: 40-70 cases per million. Average age at diagnosis is 40-50 years, with a diagnostic delay of 5-10 years. Equal prevalence in males and females.
Etiological Mechanism
>95% of cases are caused by a sporadic, benign, monoclonal GH-secreting pituitary macroadenoma (>1cm). Rare causes include ectopic GH or GHRH secretion from neuroendocrine tumors (e.g., pancreatic islet cell, bronchial carcinoid).
Primary Causes
Pituitary somatotroph adenoma
MEN-1 syndrome (Multiple Endocrine Neoplasia type 1)
McCune-Albright syndrome
Ectopic GHRH secretion (carcinoid tumor)
A mutation in the GNAS1 gene (in sporadic cases) causes constitutive activation of the stimulatory G-protein alpha subunit (Gs-alpha), leading to continuous cAMP generation and uninhibited somatotroph proliferation and GH secretion. Excess circulating GH binds to hepatic GH receptors, stimulating the synthesis and release of IGF-1. IGF-1 mediates most of the somatic growth-promoting effects, causing chondrocyte and osteoblast proliferation, leading to periosteal bone apposition, soft tissue swelling, and visceromegaly (enlarged heart, thyroid, liver). GH itself directly antagonizes insulin, leading to lipolysis and hyperglycemia.
Diagnostic Criteria & Guidelines
1. Elevated serum IGF-1 level for age and sex (best initial test). 2. Failure of GH suppression to < 1 ng/mL following a 75g oral glucose tolerance test (OGTT) (confirmatory test).
Transsphenoidal surgical resection of the pituitary adenoma is the primary and preferred treatment for cure or significant debulking.
Second-Line & Adjunctive Therapy
Medical therapy if surgery fails or is contraindicated: Somatostatin analogs (Octreotide LAR 20-30 mg IM every 4 weeks, or Lanreotide Autogel 120 mg deep SC every 4 weeks). GH receptor antagonists (Pegvisomant 10-30 mg SC daily).
Surgical & Procedural Management
Endoscopic transsphenoidal adenomectomy. Stereotactic radiosurgery (Gamma Knife) is reserved for persistent tumor remnant after surgery and medical therapy.
Patient Counseling & Advice
Advise that while surgery and medications can halt the progression and reverse soft-tissue swelling, the bony changes (jaw, hands) are irreversible. Emphasize the importance of lifelong monitoring for tumor recurrence and cardiovascular complications.
Follow-Up & Monitoring Schedule
Measure IGF-1 and GH levels 12 weeks post-op. Annual screening for cardiovascular disease (Echocardiogram). Colonoscopy every 3-5 years due to increased polyp risk. Regular visual field testing if tumor nears the optic chiasm.
Preventive Strategies
No primary prevention exists. Secondary prevention relies on early recognition of the physical changes to prevent irreversible cardiovascular and bony complications.
With successful treatment normalizing IGF-1 and GH, mortality rates return to that of the general population. Uncontrolled disease doubles the mortality rate, primarily from cardiovascular events.