Tag: HPA axis

Chronic stress and cognitive dysfunction in myalgic encephalomyelitis/chronic fatigue syndrome: HPA axis dysregulation and hippocampal plasticity

Abstract:

Cognitive dysfunction is a common and disabling clinical feature of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), often described by patients as “brain fog.” These symptoms typically manifest as difficulties in attention, memory, and concentration. Chronic stress has been proposed as an important contributing factor in ME/CFS.

The hypothalamic-pituitary-adrenal (HPA) axis plays a central role in the stress response, and prolonged adverse stress may contribute to HPA axis dysregulation, including altered cortisol rhythmicity and impaired negative feedback regulation. Such dysregulation may be associated with cognitive dysfunction in ME/CFS through mechanisms involving neuroinflammatory responses, oxidative stress, and disturbances in neurotransmitter homeostasis. Studies suggest that these alterations may affect hippocampal structure and function, thereby contributing to impaired learning and memory processes.

As a key brain region involved in cognition and stress regulation, the hippocampus may be implicated in the neurobiological mechanisms underlying cognitive dysfunction in ME/CFS. This review integrates current evidence on the potential role of HPA axis dysregulation and related neurobiological alterations in chronic stress-associated cognitive dysfunction in ME/CFS, with the aim of providing a theoretical basis for identifying potential intervention targets and informing strategies centered on HPA axis regulation.

Source: Kang H, Shao T, Shi Y, Wang S, Xiong H, Jin X, Ren J. Chronic stress and cognitive dysfunction in myalgic encephalomyelitis/chronic fatigue syndrome: HPA axis dysregulation and hippocampal plasticity. Front Neurosci. 2026 Apr 22;20:1814098. doi: 10.3389/fnins.2026.1814098. PMID: 42100733; PMCID: PMC13144083. https://pmc.ncbi.nlm.nih.gov/articles/PMC13144083/ (Full text)

Neuroendocrine signature of ME/CFS: Meta-analytic evidence for bioactive cortisol deficit and exaggerated feedback sensitivity

Abstract:

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a major clinical challenge as a complex multisystemic disorder with no well-established pathophysiological mechanism, characterized by persistent fatigue and post-exertional malaise, along with unrefreshing sleep, cognitive impairment, and impaired stress recovery. Despite decades of investigation into the hypothalamic-pituitary-adrenal (HPA) axis, a definitive neuroendocrine hallmark has remained elusive due to inconsistent findings across various cortisol matrices. Therefore, this systematic review and meta-analysis aimed to provide an integrated understanding of HPA-axis regulation in ME/CFS.

We identified 46 case-control studies (comprising 46 independent datasets, including 12 pharmacological challenge studies), involving 1388 ME/CFS patients (71.9% female; mean age 37.3 ± 6.2 years) and 1349 matched healthy controls. Meta-analyses showed lower salivary cortisol at awakening and in the morning. Reductions were also observed in 24-h urinary cortisol and hair cortisol. In pharmacological challenge tests, patients exhibited impaired cortisol release in response to adrenocorticotropic hormone (ACTH) stimulation and exaggerated suppression following glucocorticoid administration.

Collectively, these alterations indicate reduced free cortisol availability and enhanced HPA-axis negative feedback sensitivity, consistent with a hyporeactive endocrine state in ME/CFS. This neuroendocrine hypo-reactivity may underlie hallmark clinical features such as unrefreshing sleep, post-exertional malaise, and severe fatigue, as well as cognitive slowing, emotional blunting, and diminished stress resilience frequently observed in ME/CFS and related functional disorders. Integrating neuroendocrine and psychological perspectives may help clarify mechanisms of chronic stress maladaptation and inform psychobiological interventions for fatigue syndromes.

Source: Woo TW, Choi YJ, Kim JY, Lee JS, Son CG. Neuroendocrine signature of ME/CFS: Meta-analytic evidence for bioactive cortisol deficit and exaggerated feedback sensitivity. Mol Psychiatry. 2026 Apr 23. doi: 10.1038/s41380-026-03608-1. Epub ahead of print. PMID: 42026257. https://pubmed.ncbi.nlm.nih.gov/42026257/

Corticosteroids with low glucocorticoid activity as a potential therapeutic strategy for post-COVID-19 myalgic encephalomyelitis/chronic fatigue syndrome in patients with bipolar affective disorder: A case report

Abstract:

Background: The COVID-19 pandemic has led to an increase in post-acute sequelae, including myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), potentially mediated by dysfunction of the hypothalamic-pituitary-adrenal (HPA) axis. Corticosteroids are occasionally administered to ameliorate fatigue symptoms in ME/CFS; however, their psychiatric adverse effects, particularly in individuals with preexisting mood disorders, necessitate careful consideration.

Case presentation: We report the case of a 32-year-old woman with bipolar disorder who developed ME/CFS following COVID-19 infection. Initial corticosteroid therapy with betamethasone and prednisolone, agents with potent glucocorticoid receptor (GR) activity, resulted in a manic episode with psychotic features, necessitating psychiatric hospitalization. Although mood stabilization was achieved with olanzapine and valproate, corticosteroid withdrawal subsequently led to metabolic alkalosis and hypoxemia, secondary to hypothalamic hypoadrenalism. Following a comprehensive endocrinological assessment, physiological replacement therapy with hydrocortisone, characterized by relatively higher mineralocorticoid receptor (MR) activity and lower GR potency, was initiated, resulting in the resolution of physical symptoms without destabilization of psychiatric status.

Conclusion: The clinical course suggests that GR-dominant corticosteroids may exacerbate psychiatric instability in patients with mood disorders. Simultaneously, MR-favoring agents, such as hydrocortisone, may offer a safer therapeutic alternative for managing HPA axis dysfunction. This case underscores the critical role of receptor selectivity in corticosteroid therapy, particularly in patients with comorbid psychiatric conditions, and highlights the necessity for individualized treatment strategies that integrate both endocrine and neuropsychiatric considerations.

Source: Nakajima K, Ayani N, Matsuoka T, Kasahara K, Nakajima Y, Ikawa H, Kitaoka R, Akimoto T, Narumoto J. Corticosteroids with low glucocorticoid activity as a potential therapeutic strategy for post-COVID-19 myalgic encephalomyelitis/chronic fatigue syndrome in patients with bipolar affective disorder: A case report. PCN Rep. 2025 Oct 12;4(4):e70222. doi: 10.1002/pcn5.70222. PMID: 41089430; PMCID: PMC12515714.

Core features and inherent diversity of post-acute infection syndromes

Abstract:

Post-acute infection syndromes (PAIS), i.e., long-lasting pathologies subsequent to infections that do not properly resolve, have both a common core and a broad diversity of manifestations. PAIS include a group of core symptoms (pathological fatigue, cognitive problems, sleep disorders and pain) accompanied by a large set of diverse symptoms. Core and diverse additional symptoms, which can persist for years, exhibiting periods of relapses and remissions, usually start suddenly after an apparently common infection.

PAIS display highly variable clinical features depending on the nature of the initial pathogen, and to an even larger extent, on the diversity of preexisting individual terrains in which PAIS are rooted. In a first part, I discuss biological issues related to the persistence of microbial antigens, dysregulated immune responses, reactivation of latent viruses, different potential self-sustained inflammatory loops, mitochondrial dysfunction, metabolic disorders in the tryptophan- kynurenin pathway (TKP) with impact on serotonin, and consequences of a dysfunctional bidirectional microbiota-gut-brain axis.

The second part deals with the nervous system dependence of PAIS. I rely on the concept of interoception, the process by which the brain senses, integrates and interprets signals originating from within the body, and sends feebacks aimed at maintaining homeostasis. Interoception is central for understanding the origin of fatigue, dysautonomia, dysfunctioning of the hypothalamus-pituitary-adrenal (HPA) axis, and its relation with stress, inflammation or depression.

I propose that all individual predispositions leading to self-sustained vicious circles constitute building blocks that can self-assemble in many possible ways, to give rise to both core and diverse features of PAIS. A useful discrimination between different PAIS subtypes should be obtained with a composite profiling including biomarkers, questionnaires and functional tests so as to take into account PAIS multidimensionality.

Source: Trautmann A. Core features and inherent diversity of post-acute infection syndromes. Front Immunol. 2025 Jun 3;16:1509131. doi: 10.3389/fimmu.2025.1509131. PMID: 40529374; PMCID: PMC12170329. https://pmc.ncbi.nlm.nih.gov/articles/PMC12170329/ (Full text)

Brainstem Reduction and Deformation in the 4th Ventricle Cerebellar Peduncles in Long COVID Patients: Insights into Neuroinflammatory Sequelae and “Broken Bridge Syndrome”

Abstract:

Post-COVID Syndrome (PCS), also known as Long COVID, is characterized by persistent and often debilitating neurological sequelae, including fatigue, cognitive dysfunction, motor deficits, and autonomic dysregulation (Dani et al., 2021). This study investigates structural and functional alterations in the brainstem and cerebellar peduncles of individuals with PCS using diffusion tensor imaging (DTI) and volumetric analysis. Forty-four PCS patients (15 bedridden) and 14 healthy controls underwent neuroimaging. Volumetric analysis focused on 22 brainstem regions, including the superior cerebellar peduncle (SCP), middle cerebellar peduncle (MCP), periaqueductal gray (PAG), and midbrain reticular formation (mRt).

Significant volume reductions were observed in the SCP (p < .001, Hedges’ g = 3.31) and MCP (p < .001, Hedges’ g = 1.77), alongside decreased fractional anisotropy (FA) in the MCP, indicative of impaired white matter integrity. FA_Avg fractional anisotropy average tested by FreeSurfer Tracula, is an index of white matter integrity, reflecting axonal fiber density, axonal diameter and myelination. These neuroimaging findings correlated with clinical manifestations of motor incoordination, proprioceptive deficits, and autonomic instability. Furthermore, volume loss in the dorsal raphe (DR) and midbrain reticular formation suggests disruption of pain modulation and sleep-wake cycles, consistent with patient-reported symptoms.

Post-mortem studies provide supporting evidence for brainstem involvement in COVID-19. Radtke et al. (2024) reported activation of intracellular signaling pathways and release of immune mediators in brainstem regions of deceased COVID-19 patients, suggesting an attempt to inhibit viral spread. While viral genetic material was detectable, infected neurons were not observed. Matschke et al. (2020) found that microglial activation and cytotoxic T lymphocyte infiltration were predominantly localized to the brainstem and cerebellum, with limited involvement of the frontal lobe. This aligns with clinical observations implicating the brainstem in PCS pathophysiology. Cell-specific expression analysis of genes contributing to viral entry (ACE2, TMPRSS2, TPCN2, TMPRSS4, NRP1, CTSL) in the cerebral cortex showed their presence in neurons, glial cells, and endothelial cells, indicating the potential for SARS-CoV-2 infection of these cell types. Associations with autoimmune diseases with specific autoantibodies, including beta-2 and M-2 against G-protein coupled alpha-1, beta-1, beta-2 adrenoceptors against angiotensin II type 1 receptor or M1,2,3-mAChR, among others, voltage-gated calcium channels (VGCC) are known (Blitshteyn et al. 2015 and Wallukat and Schminke et al. 2014).

These findings support the “Broken Bridge Syndrome” hypothesis, positing that structural disconnections between the brainstem and cerebellum contribute to PCS symptomatology. Furthermore, we propose that chronic activation of the Extended Autonomic System (EAS), encompassing the hypothalamic-pituitary-adrenal (HPA) axis and autonomic nervous system, may perpetuate these symptoms (Goldstein, 2020). Perturbations in this system may relate to the elevation of toxic autoantibodies AABs (Beta-2 and M-2), specific epitopes of the COVID virus’s SPIKE protein and Cytokine storm of IL-1, IL-6, and IL-8 in their increased numbers (1,000->10,000)

Further research is warranted to elucidate the underlying neuroinflammatory mechanisms, EAS dysregulation, and potential therapeutic interventions for PCS

Source: Ziaja Peter Christof, Young Yvette Susanne, Stark Sadre-Chirazi Michael, Lindner Thomas, Zurék Grzegorz, Sedlacik Jan. Brainstem Reduction and Deformation in the 4th Ventricle Cerebellar Peduncles in Long COVID Patients: Insights into Neuroinflammatory Sequelae and “Broken Bridge Syndrome” medRxiv 2025.04.08.25325108; doi: https://doi.org/10.1101/2025.04.08.25325108 https://www.medrxiv.org/content/10.1101/2025.04.08.25325108v1.full-text (Full text)

Research progress in the treatment of chronic fatigue syndrome through interventions targeting the hypothalamus-pituitary-adrenal axis

Abstract:

Chronic fatigue syndrome (CFS) causes great harm to individuals and society. Elucidating the pathogenesis of CFS and developing safe and effective treatments are urgently needed. This paper reviews the functional changes in the hypothalamus-pituitary-adrenal (HPA) axis in patients with CFS and the associated neuroendocrine mechanisms. Despite some controversy, the current mainstream research evidence indicates that CFS patients have mild hypocortisolism, weakened daily variation in cortisol, a weakened response to the HPA axis, and an increase in negative feedback of the HPA axis. The relationship between dysfunction of the HPA axis and the typical symptoms of CFS are discussed, and the current treatment methods are reviewed.

Source: Yi-Dan Zhang, Li-Na Wang. Research progress in the treatment of chronic fatigue syndrome through interventions targeting the hypothalamus-pituitary-adrenal axis. Front. Endocrinol., 09 April 2024, Sec. Neuroendocrine Science, Volume 15 – 2024 | https://doi.org/10.3389/fendo.2024.1373748 https://www.frontiersin.org/journals/endocrinology/articles/10.3389/fendo.2024.1373748/full

Central 5-HTergic hyperactivity induces myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)-like pathophysiology

Abstract:

Objectives: Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a significant medical challenge, with no indisputable pathophysiological mechanism identified to date.

Methods: Based on clinical clues, we hypothesized that 5-hydroxytryptamine (5-HT) hyperactivation is implicated in the pathogenic causes of ME/CFS and the associated symptoms. We experimentally evaluated this hypothesis in a series of mouse models.

Results: High-dose selective serotonin reuptake inhibitor (SSRI) treatment induced intra- and extracellular serotonin spillover in the dorsal raphe nuclei of mice. This condition resulted in severe fatigue (rota-rod, fatigue rotating wheel and home-cage activity tests) and ME/CFS-associated symptoms (nest building, plantar and open field test), along with dysfunction in the hypothalamic-pituitary-adrenal (HPA) axis response to exercise challenge. These ME/CFS-like features induced by excess serotonin were additionally verified using both a 5-HT synthesis inhibitor and viral vector for Htr1a (5-HT1A receptor) gene knockdown.

Conclusions: Our findings support the involvement of 5-HTergic hyperactivity in the pathophysiology of ME/CFS. This ME/CFS-mimicking animal model would be useful for understanding ME/CFS biology and its therapeutic approaches.

Source: Lee JS, Kang JY, Park SY, Hwang SJ, Bae SJ, Son CG. Central 5-HTergic hyperactivity induces myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)-like pathophysiology. J Transl Med. 2024 Jan 8;22(1):34. doi: 10.1186/s12967-023-04808-x. PMID: 38191373. https://translational-medicine.biomedcentral.com/articles/10.1186/s12967-023-04808-x (Full text)

Treatment and outcomes of 95 post-Covid patients with an antidepressant and neurobiological explanations

Abstract:

After Covid-19 infection, 12.5% develop a post-Covid-syndrome. Symptoms affect numerous organ systems, but after one year they are mainly neurological and neuropsychiatric in nature. There is evidence that treatment with selective serotonin reuptake inhibitors (SSRIs) during Covid-19 infection decreases the likelihood of a post-Covid condition, but there is no known research on treating post-Covid syndrome itself with SSRIs.

This study used an exploratory questionnaire and found that 63,4% of 95 post-Covid syndrome patients reported a reasonably good to strong response to an SSRI. Outcomes were measured with three different measures that correlated strongly with each other. Brainfog and sensory overload decreased the most. Patients experienced improved well-being. The response to SSRIs in post-Covid conditions was explained by seven possible neurobiological mechanisms as reported in the recent literature. The promising results of this study should be followed by a randomized controlled trial.

Source: Rus CC, de Vries B, Vries IE, Nutma I, Kooij JJS. Treatment and outcomes of 95 post-Covid patients with an antidepressant and neurobiological explanations. Research Square; 2023. DOI: 10.21203/rs.3.rs-3153645/v1. https://assets.researchsquare.com/files/rs-3153645/v1/ffdd7433-9013-41d5-9f16-154074f3a204.pdf (Full text)

Synbiotic Supplementation Improves Quality of Life and Inmunoneuroendocrine Response in Patients with Fibromyalgia: Influence of Codiagnosis with Chronic Fatigue Syndrome

Abstract:

Fibromyalgia (FM) and chronic fatigue syndrome (CFS) are two medical conditions in which pain, fatigue, immune/inflammatory dysregulation, as well as various mental health disorders predominate in the diagnosis, without evidence of a clear consensus on the treatment of FM and CFS.
The main aim of this research was to analyse the possible effects of a synbiotic (Synbiotic, Gasteel Plus® (Heel España S.A.U.), through the study of pro-inflammatory/anti-inflammatory cytokines (IL-8/IL-10) and neuroendocrine biomarkers (cortisol and DHEA), in order to evaluate the interaction between inflammatory and stress responses mediated by the cytokine-HPA (hypothalamic-pituitary-adrenal) axis, as well as mental and physical health using body composition analysis, accelerometry and previously validated questionnaires.
The participants were women diagnosed with FM with or without a diagnostic of CFS. Each participant was evaluated at baseline and after the intervention, which lasted one month. Synbiotic intervention decreased levels of perceived stress, anxiety and depression, as well as improved quality of life during daily activities. In addition, the synbiotic generated an activation of HPA axis (physiological cortisol release) that can compensate the increased inflammatory status (elevated IL-8) observed at baseline in FM patients. There were no detrimental changes in body composition or sleep parameters, as well as in the most of the activity/sedentarism-related parameters studied by accelerometry.
It is concluded that synbiotic nutritional supplements can improve the dysregulated immunoneuroendocrine interaction involving inflammatory and stress responses in women diagnosed with FM, particularly in those without a previous CFS diagnostic; as well as their perceived of levels stress, anxiety, depression and quality of life.
Source: Hinchado MD, Quero-Calero CD, Otero E, Gálvez I, Ortega E. Synbiotic Supplementation Improves Quality of Life and Inmunoneuroendocrine Response in Patients with Fibromyalgia: Influence of Codiagnosis with Chronic Fatigue Syndrome. Nutrients. 2023; 15(7):1591. https://doi.org/10.3390/nu15071591 https://www.mdpi.com/2072-6643/15/7/1591 (Full text)

The Link Between Empty Sella Syndrome, Fibromyalgia, and Chronic Fatigue Syndrome: The Role of Increased Cerebrospinal Fluid Pressure

Abstract:

The etiopathogenesis of fibromyalgia (FM) and chronic fatigue syndrome (CFS) is not yet elucidated. Hypothalamo-pituitary-adrenal (HPA) axis dysfunction is reflected in the hormonal disturbances found in FM and CFS. Some study groups have introduced a novel hypothesis that moderate or intermittent intracranial hypertension may be involved in the etiopathogenesis of FM and CFS.

In these conditions, hormonal disturbances may be caused by the mechanical effect of increased cerebrospinal fluid pressure, which hampers blood flow in the pituitary gland. Severe intracranial pressure may compress the pituitary gland, resulting in primary empty sella (ES), potentially leading to pituitary hormone deficiencies.

The aim of this narrative review was to explore whether similar hormonal changes and symptoms exist between primary ES and FM or CFS and to link them to cerebrospinal fluid pressure dysregulation. A thorough search of the PubMed and Web of Science databases and the reference lists of the included studies revealed that several clinical characteristics were more prevalent in primary ES, FM or CFS patients than in controls, including increased cerebrospinal fluid pressure, obesity, female sex, headaches and migraine, fatigue, visual disturbances (visual acuity and eye motility abnormalities), vestibulocochlear disturbances (vertigo and neurosensorial hearing loss), and bodily pain (radicular pain and small-fiber neuropathy).

Furthermore, challenge tests of the pituitary gland showed similar abnormalities in all three conditions: blunted adrenocorticotropic hormone, cortisol, growth hormone, luteinizing hormone, and thyroid stimulating hormone responses and an increased prolactin response. The findings of this narrative review provide further support for the hypothesis that moderately or intermittently increased cerebrospinal fluid pressure is involved in the pathogenesis of FM and CFS and should stimulate further research into the etiopathogenesis of these conditions.

Source: Hulens M, Dankaerts W, Rasschaert R, Bruyninckx F, De Mulder P, Bervoets C. The Link Between Empty Sella Syndrome, Fibromyalgia, and Chronic Fatigue Syndrome: The Role of Increased Cerebrospinal Fluid Pressure. J Pain Res. 2023;16:205-219
https://doi.org/10.2147/JPR.S394321 https://www.dovepress.com/the-link-between-empty-sella-syndrome-fibromyalgia-and-chronic-fatigue-peer-reviewed-fulltext-article-JPR (Full text)