Systemic illnesses, including catabolic states, hepatic or renal failure, malnutrition, and diabetes mellitus, are known to decrease insulin-like growth factor-1 levels and may result in false-negative values in patients with acromegaly A low insulin-like growth factor-1 level does not exclude acromegaly in a patient with supportive clinical features and poorly controlled diabetes. The gene discussed is IGF1; the disease is diabetes mellitus.