Current Challenges and Future Directions in the Assessment of Glucocorticoid Status.

Glucocorticoid hormones (GC) are secreted in a circadian and ultradian rhythm and play a critical role in maintaining physiological homeostasis, with both excess and insufficient GC associated with adverse effects on health. Current assessment of GC status is primarily clinical, often in conjunction with serum cortisol values, which may be stimulated or suppressed depending on the GC disturbance being assessed. In the setting of extreme perturbations in cortisol levels i.e. markedly low or high levels, symptoms and signs of GC dysfunction may be overt. However, when disturbances in cortisol GC status values are less extreme, such as when assessing optimization of a GC replacement regimen, signs and symptoms can be more subtle or non-specific. Current tools for assessing GC status, are best suited to identifying profound disturbances but may lack sensitivity for confirming optimal GC status. Moreover, single cortisol values do not necessarily reflect an individual's GC status, as they are subject to inter- and intra-individual variation, do not take into account the pulsatile nature of cortisol secretion, variation in binding proteins, or local tissue concentrations as dictated by 11βeta-hydroxysteroid dehydrogenase (11β-HSD) activity, as well as GC receptor sensitivity. In the present review, we evaluate possible alternative methods for the assessment of GC status that do not solely rely on measurement of circulating cortisol levels. We discuss the potential of changes in metabolomic profiles, miRNA, gene expression, epigenetic, and other novel biomarkers such as GDF-15 and osteocalcin, that could in future aid in the objective classification of GC status.