Origin and significance of the heterogeneity of protein hormones

The heterogeneity of circulating protein hormone is the result of multiple steps including gene expression, mRNA maturation, post-translational processing and peripheral catabolism. As a consequence of these cumulative events, it seems difficult to evaluate the endocrine function by using specific radioimmunoassays for each circulating variant of a protein hormone. Moreover, the discovery of new molecular variants of protein hormones with unknown biological significance complicates the standardization and the clinical interpretation of immunoassays.