4 Diagnostic challenges in acromegaly: a case-based review

Acromegaly is a rare, chronic condition caused by sustained and unregulated oversecretion of growth hormone (GH), usually attributed to a pituitary adenoma. Prolonged exposure to excessive amounts of GH and its target hormone, insulin-like growth factor-1 (IGF-1), results in pronounced metabolic changes and tissue enlargement that ultimately lead to increased morbidity and early mortality. As early diagnosis of acromegaly can have substantial beneficial effects on quality of life and overall survival for patients, it is important that the tests used to diagnose the condition are accurate, with highly reproducible results. The first kits used to measure GH and IGF-1 were radioimmunoassay, with many limitations that necessitated the development of more sensitive tools. Newer assays, although better than previous assays, are far from ideal. Simple changes that may improve the testing process include the adoption of mass units for GH interpretation and the use of a single recombinant calibrant. Furthermore, the conversion factors and reference ranges used to describe the normal limits for GH and IGF-1 levels require refinement. Physicians should be aware of the GH and IGF-1 assays used in their reference laboratories, and ensure that they know the appropriate assay cut-off values, to avoid misinterpreting results.