Acromegaly is caused by an excess of growth hormone (GH) production by an adenoma. Over 90% of patients with acromegaly have a benign monoclonal pituitary adenoma. This increase in growth hormone leads to a subsequent increased insulin-like growth factor 1 (IGF-1) levels, which have many systemic effects. Anatomic and physiologic changes occur slowly. Consequently, acromegaly is often undetected until changes in outward appearance are present or the pituitary gland has grown to compress surrounding structures.
The outward changes vary with the duration of untreated disease. Frontal bossing, hypertrichosis, hyperhidrosis, and hyperpigmentation accompany macroglossia and prognathism. Posterior pharyngeal structures such as the epiglottis and the arylepiglottic folds may undergo hypertrophy. The vocal cords swell causing a deeper voice. Swelling also occurs in the nose, lips, ears, hands, and feet. The upper airway changes lead to a challenging airway and intubation should be carefully planned.
Physiologic changes involve most organ systems. Cardiovascular manifestations occur in about 60% of patients with acromegaly. Hypertension is often present and can exacerbate the effects to other organ systems. Elevated IGF-1 levels lead to an initial hyperkinetic state, with concentric biventricular hypertrophy. This state is followed by diastolic dysfunction due to persistent wall ventricular wall thickening, and eventually systolic failure.
Respiratory changes follow two main pathologies: sleep apnea and impaired respiratory function. Sleep apnea is most often obstructive in nature due to upper airway narrowing. Untreated sleep apnea can exacerbate underlying cardiac dysfunction. Furthermore, vertebral and costal changes lead to a “barrel chest” formation, leading to a slight restrictive pattern. Coupled with impaired expiration due to upper airway narrowing, lung volumes increase and may have subclinical hypoxemia.
Large joint arthropathies are also very common. Once the epiphyseal plates have fused, further bursts of GH and IGF-1 hormones lead to further cartilage development. The initially functional joints become disarticulated, and movement leads to localized injury and pain.
Excess growth hormone also leads to insulin resistance and diabetes. Diabetes is often present in patients with acromegaly. It takes time to develop and is often seen in patients who are older with a longer duration of disease. If the acromegaly is treated, this insulin resistance has a good chance of resolving.
Gastrointestinal manifestations of acromegaly include increased risk of colon cancer, adenomatous polyps, dolichocolon and diverticulosis. The increased secondary cancer risks are thought to be yet another effect of IGF-1. These risks are only present in patients who are not actively treated for acromegaly. Dolichocolon, an unusually long colon, is associated with volvulus, but does not have to be addressed preemptively. Renal failure can develop as well due to direct effects of IGF-1 on the kidneys, causing an increased size and detrimental changes to its electrolyte management pattern.
After fasting, serum levels of GH and IGF-1 are measured. ...