E3 PreliminaryPreliminaryPEM not requiredMechanisticPeer-reviewedMachine draft
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Inclusion of the glucocorticoid receptor in a hypothalamic pituitary adrenal axis model reveals bistability.
Gupta, Shakti, Aslakson, Eric, Gurbaxani, Brian M et al. · Theoretical biology & medical modelling · 2007 · DOI
Quick Summary
This study created a mathematical model of the body's stress-response system (the HPA axis) that helps explain why some people with chronic stress develop low cortisol levels. The model shows that when stress is repeated over a long time, the body can get 'stuck' in a low-cortisol state, similar to what happens in ME/CFS. The research suggests this happens because of how cortisol's receptor proteins build up and change how the stress system works.
Why It Matters
This study offers a plausible biological mechanism for the HPA axis dysfunction and low cortisol observed in ME/CFS patients. Understanding how chronic stress can 'lock' the stress system into an abnormal state may guide development of new treatments. The model bridges the gap between observed HPA axis abnormalities in ME/CFS and the cellular processes that cause them.
Observed Findings
Mathematical model predicts two stable cortisol steady states (low and high) are possible in the HPA axis when GR homodimerization is included.
Short-term stress produces small, reversible changes in GR concentration that quickly return to baseline.
Chronic repeated stress produces persistent, elevated GR concentration that does not return to normal levels.
High pituitary GR concentration corresponds to reduced steady-state cortisol production.
The model produces hypocortisolism consistent with observations in some ME/CFS patients.
Inferred Conclusions
HPA axis bistability driven by nonlinear GR kinetics provides a mechanistic explanation for how chronic stress can trap the system in a dysregulated, hypocortisolemic state.
Increased pituitary GR concentration enhances negative feedback on the hypothalamus, maintaining low cortisol production.
The model suggests that ME/CFS-associated hypocortisolism may result from stress-induced transition to an alternative HPA axis equilibrium point.
Nonlinear dynamics of glucocorticoid receptor regulation are essential for understanding HPA dysfunction in stress-related disorders.
Remaining Questions
Does HPA axis bistability actually occur in ME/CFS patients, and can it be measured experimentally?
What This Study Does Not Prove
This is a mathematical model and does not provide direct experimental evidence that this bistability mechanism actually occurs in ME/CFS patients. The study does not prove that low cortisol in ME/CFS is caused by this mechanism—it demonstrates one theoretically plausible pathway. Clinical validation through patient studies measuring GR expression and HPA axis dynamics would be needed to confirm the model's relevance.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →