CLINICAL AND MEDICAL DIAGNOSIS OF ACROMEGALY

The biochemical diagnosis of acromegaly and assessment of the clinical activity of the disease can he made by measurement of the insulin lik e growth factor-l (IGF-I) concentration in the serum. False positive i ncreases seldom occur. This determination has largely replaced measure ment of the growth hormone (GH) response to the oral administration of glucose, which in normal individuals suppresses to less than 2 mu g/L . In normally fed individuals with normal liver and renal function, ci rculating IGF-I levels reflect the integrated effect of GH at the tiss ue level and also correlate with mean 24 hour GH levels. Measurement o f the IGF-I concentration differentiates subjects with active untreate d acromegaly from normal individuals, but the serum IGF-I level also r eflects the clinical activity of the disease. However, it remains deba table whether this particular parameter represents most faithfully the course of the disease. Computed tomography and magnetic resonance ima ging have greatly facilitated the diagnosis of pituitary abnormalities in acromegalic patients. Evidence of a pituitary tumor is found in al most all patients. Most adenomas are larger than 10 mm in diameter at the time of diagnosis, and extrasellar extension is present in approxi mately one third of cases. (C) 1995 by W.B. Saunders Company