Correlation between brain interstitial and total serum cortisol levels in traumatic brain injury. A preliminary study

Advancements in Cortisol Detection: From Conventional Methods to Next-Generation Technologies for Enhanced Hormone Monitoring

The hormone cortisol, released as the end-product of the hypothalamic-pituitary-adrenal (HPA) axis, has a well-characterized circadian rhythm that enables an allostatic response to external stressors. When the pattern of secretion is disrupted, cortisol levels are chronically elevated, contributing to diseases such as heart attacks, strokes, mental health disorders, and diabetes. The diagnosis of chronic stress and stress related disorders depends upon accurate measurement of cortisol levels; currently, it is quantified using mass spectroscopy or immunoassay, in specialized laboratories with trained personnel. However, these methods are time-consuming, expensive and are unable to capture the dynamic biorhythm of the hormone. This critical review traces the path of cortisol detection from traditional laboratory-based methods to decentralised cortisol monitoring biosensors. A complete picture of cortisol biology and pathophysiology is provided, and the importance of precision medicine style monitoring of cortisol is highlighted. Antibody-based immunoassays still dominate the pipeline of development of point-of-care biosensors; new capture molecules such as aptamers and molecularly imprinted polymers (MIPs) combined with technologies such as microfluidics, wearable electronics, and quantum dots offer improvements to limit of detection (LoD), specificity, and a shift toward rapid or continuous measurements. While a variety of different sensors and devices have been proposed, there still exists a need to produce quantitative tests for cortisol ─ using either rapid or continuous monitoring devices that can enable a personalized medicine approach to stress management. This can be addressed by synergistic combinations of technologies that can leverage low sample volumes, relevant limit of detection and rapid testing time, to better account for cortisol's shifting biorhythm. Trends in cortisol diagnostics toward rapid and continuous monitoring of hormones are highlighted, along with insights into choice of sample matrix.

INVITED REVIEW: The usefulness of measuring glucocorticoids for assessing animal welfare

Glucocorticoids (corticosterone in birds and rodents and cortisol in all other mammals) are glucoregulatory hormones that are synthesized in response to a range of stimuli including stress and are regularly measured in the assessment of animal welfare. Glucocorticoids have many normal or non-stress-related functions, and glucocorticoid synthesis can increase in response to pleasure, excitement, and arousal as well as fear, anxiety, and pain. Often, when assessing animal welfare, little consideration is given to normal non-stress-related glucocorticoid functions or the complex mechanisms that regulate the effects of glucocorticoids on physiology. In addition, it is rarely acknowledged that increased glucocorticoid synthesis can indicate positive welfare states or that a stress response can increase fitness and improve the welfare of an animal. In this paper, we review how and when glucocorticoid synthesis increases, the actions mediated through type I and type II glucocorticoid receptors, the importance of corticosteroid-binding globulin, the role of 11 β-hydroxysteroid dehydrogenase, and the key aspects of neurophysiology relevant to activating the hypothalamo-pituitary-adrenal axis. This is discussed in the context of animal welfare assessment, particularly under the biological functioning and affective states frameworks. We contend that extending the assessment of animal welfare to key brain regions afferent to the hypothalamus and incorporating the aspects of glucocorticoid physiology that affect change in target tissue will advance animal welfare science and inspire more comprehensive assessment of the welfare of animals.

Heart rate variability and serum level of insulin-like growth factor-1 are correlated with symptoms of emotional disorders in patients suffering a mild traumatic brain injury

OBJECTIVE

Patients who have experienced a mild traumatic brain injury (mTBI) are susceptible to symptoms of anxiety or depression. To explore the potential biomarkers for emotional disorders in mTBI patients, we analyzed the frequency domain of heart rate variability (HRV) and serum concentrations of four neurohormones.

METHODS

We assessed mTBI patients on their first visit and follow-up. Symptoms were evaluated by the Beck Anxiety Inventory and the Beck Depression Inventory, respectively. Serum levels of adrenocorticotropic hormone (ACTH), melatonin, cortisol, and insulin-like growth factor (IGF)-1 and HRV follow-ups were measured and compared.

RESULTS

mTBI patients were more vulnerable to symptoms of anxiety or depression than healthy controls. Reduced HRV was noted in mTBI patients compared to healthy controls. The mTBI patients demonstrated higher serum levels of ACTH, lower IGF-1 compared to healthy controls. In correlation analysis, only IGF-1 was positively correlated with HRV in mTBI patients. Both HRV and IGF-1 were correlated with symptom of depression while only HRV was correlated with symptom of anxiety in mTBI patients.

CONCLUSIONS

We infer that HRV may be more significantly correlated with emotional disorders than is IGF-1 in mTBI patients.

SIGNIFICANCE

The study is relevant for specific diagnostic markers in mTBI patients.

Regulation of cortisol bioavailability--effects on hormone measurement and action

Routine assessment of the hypothalamic-pituitary-adrenal axis relies on the measurement of total serum cortisol levels. However, most cortisol in serum is bound to corticosteroid-binding globulin (CBG) and albumin, and changes in the structure or circulating levels of binding proteins markedly affect measured total serum cortisol levels. Furthermore, high-affinity binding to CBG is predicted to affect the availability of cortisol for the glucocorticoid receptor. CBG is a substrate for activated neutrophil elastase, which cleaves the binding protein and results in the release of cortisol at sites of inflammation, enhancing its tissue-specific anti-inflammatory effects. Further tissue-specific modulation of cortisol availability is conferred by corticosteroid 11β-dehydrogenase. Direct assessment of tissue levels of bioavailable cortisol is not clinically practicable and measurement of total serum cortisol levels is of limited value in clinical conditions that alter prereceptor glucocorticoid bioavailability. Bioavailable cortisol can, however, be measured indirectly at systemic, extracellular tissue and cell levels, using novel techniques that have provided new insight into the transport, metabolism and biological action of glucocorticoids. A more physiologically informative approach is, therefore, now possible in the assessment of the hypothalamic-pituitary-adrenal axis, which could prove useful in clinical practice.

Loss of cortisol circadian rhythm in patients with traumatic brain injury: a microdialysis evaluation

BACKGROUND

Traumatic brain injury (TBI) is commonly associated with disturbances of the hypothalamic-pituitary-adrenal axis secretion. Cerebral microdialysis techniques have been recently applied to measure brain interstitial cortisol levels.

METHODS

We evaluated for the first time the circadian rhythm of cortisol secretion at 08:00, 16:00, and 24:00 h in the acute phase of TBI by determination of total serum and brain interstitial cortisol levels (microdialysis samples) in 10 patients with TBI. Non-parametric Friedman's two way analysis of variance test was used.

RESULTS

Mean age was 29.8 ± 13.6 years. Median Glasgow Coma Scale score after resuscitation was 5 (range 3-10). No differences were found in total serum (P = 0.26) and brain interstitial cortisol (P = 0.77) in the whole sample. Intraindividual analysis showed that circadian variability was lost in all patients, both in serum and brain interstitial cortisol samples in the acute phase after TBI.

CONCLUSION

In our series, circadian variability of cortisol evaluated by serum and cerebral microdialysis samples seems to be lost in TBI patients.