• The term acromegaly comes from the Greek words for "extremities" and "enlargement."
• Acromegaly is a condition caused by an abnormal overproduction of growth hormone (GH) from the anterior pituitary, usually by a pituitary tumor. The result is an overgrowth of skeletal, soft, and connective tissues. Enlargement is seen in:
  • Major organs including the heart, lungs, liver, and kidney
  • Hands, feet, jaw, and tongue
  • Airway anatomy including the tongue, epiglottis, mandible, and generalized soft tissue (making airway management potentially difficult)

• No major risk factors
• Weak risk factors include:
  • MEN type I syndrome
  • McCune–Albright syndrome
  • Isolated familial acromegaly
  • Carney complex
  • Family history of aryl hydrocarbon-receptor interacting protein (AIP) mutation

• Hypothalamus: Growth hormone-releasing hormone (GHRH) is produced and secreted by the hypothalamus via the hypophyseal tract to the anterior pituitary gland (as is somatostatin).
• Pituitary gland: GHRH stimulates the anterior pituitary gland to produce and secrete GH into the bloodstream, whereas somatostatin inhibits GH production and secretion.
• Tissues: GH travels to and stimulates the liver to produce another hormone called insulin-like growth factor 1 (IGF-1). IGF-1, in turn, promotes growth of bone and other tissues.
• "Feedback loop": Normally, levels of GHRH, GH, somatostatin, and IGF-1 are tightly controlled by each other. Levels are affected by: Sleep, exercise, stress, food intake, and blood sugar levels.
• Excessive GH results from pituitary adenomas in >95% of cases. Secretion of GH by a pituitary tumor is not controlled by the feedback loop resulting in excessive IGF-1 with subsequent abnormal tissue growth.
  • Carbohydrate and fat processing is affected causing diabetes and high levels of fats in the blood. This, in turn, can lead to atherosclerosis and heart disease.
  • Myocardial growth can result in conduction disturbances.
  • Hepatomegaly
  • Kidneys: Positive fluid balance may be due to chronic hypertension, causing vasoconstriction, preoperative hypovolemia, lower cardiac output, fluid volume dysautoregulation, and/or renal dysfunction.
  • Lungs: Lower arterial pH
  • Tumors can also grow to considerable size and cause problems by pressing on and invading surrounding tissues.
• Gigantism is the term used when acromegaly occurs in children.

• Patients with acromegaly may have glottic or subglottic stenosis, nasal turbinate enlargement, vocal cord thickening, or recurrent laryngeal nerve involvement. Be aware of the potential for a difficult airway, perform a careful exam, and consider having backup airway devices available.
• Address comorbid conditions including diabetes, hypertension, and cardiac disease.

• May be divided into 2 groups: Tumor compression of surrounding tissues or those caused by excess GH and IGF-1 in the blood. Compression of surrounding tissues can present as headaches or partial loss of vision in one or both eyes. Bitemporal hemianopsia is due to pressure on the optic chiasm.
• Pituitary tumors also can damage the pituitary gland itself, disrupting hormone production. Hormone imbalances are responsible for symptoms such as impotence, low sex drive, and changes in the menstrual cycle.
• Symptoms due to excess GH or IGF-1 include increase in ring size or tightness of rings ("sausage-like" fingers), shoe size, sweating, jaw prominence, as well as coarseness or thickening of facial features (especially the nose), macroglossia, or skin tags.

• Octreotide is a somatostatin analog that inhibits GH secretion. It is capable of causing GI side effects such as nausea, bloating, and gas in up to 30% of patients.
• Dopamine agonists, bromocriptine and cabergoline, work at the level of the pituitary to reduce GH and subsequent IGF-1 secretion.
• Pegvisomant is a GH receptor blocker and a new category of drugs. Studies have shown that it normalized IGF-1 levels in >90% of people treated. Side effects include reaction at the injection site, sweating, headache, and fatigue.

• Hypertension
• Diabetes mellitus
• Arthritis
• Colonic polyps
• Coronary artery disease
• Conduction disturbances

• Severe symptoms such as CHF or critical aortic stenosis
• Returning GH levels to normal can reduce the incidence of upper respiratory tract complications. Regression of the mucosal hyperplasia and thickening could be achieved preoperatively.

• Biochemical criteria:
  • Elevated age- and sex-matched plasma IGF-1, random plasma GH >0.4 mcg/L, and lack of GH suppression below 1 mcg/L following an oral glucose load
  • Severity is judged according to GH levels, which correlate with the tumor mass.
• Imaging criteria: Severity of pituitary adenoma judged according to:
  • Pituitary tumor volume
  • Suprasellar extension and compression of neural structures
  • Invasion of sphenoid bone and cavernous sinuses
• Pathology criteria: Positive GH immunostaining confirms the diagnosis of a pituitary GH-secreting adenoma. On the basis of the number of cytoplasmic granules, somatotroph adenomas are divided into 2 types:
  • Densely granulated
  • Sparsely granulated (more aggressive)

• Consider supplemental oxygen (nasal cannula, face mask)
• Prepare for the potential backward displacement of the already large tongue post-extubation that may cause respiratory compromise.

• Airway difficulties
• Mild perioperative metabolic problems occur with respect to blood glucose and fluid balance.

• Cushing Syndrome
• Diabetes Mellitus
• Difficult Airway

253.0 Acromegaly and gigantism

E22.0 Acromegaly and pituitary gigantism

Adam Thaler , DO