The importance of dynamic signalling for endocrine regulation and drug development: relevance for glucocorticoid hormones

Dual-release hydrocortisone improves body composition and the glucometabolic profile in patients with secondary adrenal insufficiency

PURPOSE

Studies have suggested improved metabolic profiles in patients with adrenal insufficiency treated with dual-release hydrocortisone (DR-HC) compared with conventional hydrocortisone (C-HC). This study investigates the effect of DR-HC compared with C-HC treatment on five health variables: diurnal salivary cortisol/cortisone, body composition, bone health, glucose metabolism, lipids, and blood pressure.

METHODS

Prospective study of 27 participants (24 men) with secondary adrenal insufficiency with measurements during stable C-HC and 16 weeks after treatment switch to DR-HC.

OUTCOMES

Diurnal salivary-cortisol/cortisone, body composition assessed by Dual-Energy X-ray absorptiometry scan, bone status indices (serum type I N-terminal procollagen [PINP], collagen type I cross-linked C-telopeptide [CTX], osteocalcin, receptor activator kappa-B [RANK] ligand, osteoprotegerin, and sclerostin), lipids, haemoglobin A1c (HbA1c), and 24-hour blood pressure.

RESULTS

After the switch to DR-HC, the diurnal salivary-cortisol area under the curve (AUC) decreased non-significantly (mean difference: -55.9 nmol/L/day, P = 0.06). The salivary-cortisone-AUC was unchanged. Late-evening salivary-cortisol and cortisone were lower (-1.6 and -1.7 nmol/L, P = 0.002 and 0.004). Total and abdominal fat mass (-1.5 and -0.5 kg, P = 0.003 and 0.02), HbA1c (-1.2 mmol/mol, P = 0.02), and osteocalcin decreased (-7.0 µg/L, P = 0.03) whereas sclerostin increased (+41.1 pg/mL, P = 0.0001). The remaining bone status indices, lipids, and blood pressure were unchanged.

CONCLUSION

This study suggests that switching to DR-HC leads to lower late-evening cortisol/cortisone exposure and a more favourable metabolic profile and body composition. In contrast, decreased osteocalcin with increasing sclerostin might indicate a negative impact on bones.

CLINICAL TRIAL REGISTRATION

EudraCT201400203932.

Electrochemical sensors for cortisol detection: Principles, designs, fabrication, and characterisation

Psychological stress is a major factor contributing to health discrepancies among individuals. Sustained exposure to stress triggers signalling pathways in the brain, which leading to the release of stress hormones in the body. Cortisol, a steroid hormone, is a significant biomarker for stress management due to its responsibility in the body's reply to stress. The release of cortisol in bloodstream prepares the body for a "fight or flight" response by increasing heart rate, blood pressure, metabolism, and suppressing the immune system. Detecting cortisol in biological samples is crucial for understanding its role in stress and personalized healthcare. Traditional techniques for cortisol detection have limitations, prompting researchers to explore alternative strategies. Electrochemical sensing has emerged as a reliable method for point-of-care (POC) cortisol detection. This review focuses on the progress made in electrochemical sensors for cortisol detection, covering their design, principle, and electroanalytical methodologies. The analytical performance of these sensors is also analysed and summarized. Despite significant advancements, the development of electrochemical cortisol sensors faces challenges such as biofouling, sample preparation, sensitivity, flexibility, stability, and recognition layer performance. Therefore, the need to develop more sensitive electrodes and materials is emphasized. Finally, we discussed the potential strategies for electrode design and provides examples of sensing approaches. Moreover, the encounters of translating research into real world applications are addressed.

Interpretation of Steroid Biomarkers in 21-Hydroxylase Deficiency and Their Use in Disease Management

The most common form of congenital adrenal hyperplasia is 21-hydroxylase deficiency (21OHD), which in the classic (severe) form occurs in roughly 1:16 000 newborns worldwide. Lifelong treatment consists of replacing cortisol and aldosterone deficiencies, and supraphysiological dosing schedules are typically employed to simultaneously attenuate production of adrenal-derived androgens. Glucocorticoid titration in 21OHD is challenging as it must balance the consequences of androgen excess vs those from chronic high glucocorticoid exposure, which are further complicated by interindividual variability in cortisol kinetics and glucocorticoid sensitivity. Clinical assessment and biochemical parameters are both used to guide therapy, but the specific purpose and goals of each biomarker vary with age and clinical context. Here we review the approach to medication titration for children and adults with classic 21OHD, with an emphasis on how to interpret adrenal biomarker values in guiding this process. In parallel, we illustrate how an understanding of the pathophysiologic and pharmacologic principles can be used to avoid and to correct complications of this disease and consequences of its management using existing treatment options.

Mini-review: pump therapy in endocrinology & metabolism beyond diabetes

The first pump developed by Dr. Kadish and his team in 1963 aimed to "continue subcutaneous insulin infusion". The number of patients using insulin pumps has increased since the 1980s. This historical perspective has labeled pump therapy in endocrinology and metabolism synonymous with insulin pumps. However, certain other hormonal disorders might also benefit from this kind of treatment. Pump therapy is currently the best approach to achieve physiological mimicry. Furthermore, it may help in overcoming pharmacokinetic issues or allergies. Until now, hormone replacement via pumps has been a salvage method for complex cases at the expense of increased costs. However, it is believed that applications of pump treatment will widen in the future owing to the rapidly evolving technology. In this mini review, data on pump use for patients with adrenal insufficiency, hypogonadism, hypoparathyroidism, congenital adrenal hyperplasia, and congenital hyperinsulinism have been briefly summarized. The study has aimed at covering all the relevant clinical studies and important case reports/series. METHODS: A systematic literature search has been conducted on PubMed database seeking articles published until May 2021 using a combination of the following Medical Subject Headings terms and keywords: pump "OR" continue infusion "AND" (adrenal insufficiency "OR" Addison "OR" hydrocortisone "OR" hypoparathyroidism "OR teriparatide" "OR" somatostatin "OR" hypogonadism "OR" hypoglycemia "OR" endocrinology "OR" hormone replacement). In addition, the reference publications in the identified articles have also been reviewed.

Adolescent Development of Biological Rhythms in Female Rats: Estradiol Dependence and Effects of Combined Contraceptives

Adolescence is a period of continuous development, including the maturation of endogenous rhythms across systems and timescales. Although, these dynamic changes are well-recognized, their continuous structure and hormonal dependence have not been systematically characterized. Given the well-established link between core body temperature (CBT) and reproductive hormones in adults, we hypothesized that high-resolution CBT can be applied to passively monitor pubertal development and disruption with high fidelity. To examine this possibility, we used signal processing to investigate the trajectory of CBT rhythms at the within-day (ultradian), daily (circadian), and ovulatory timescales, their dependence on estradiol (E2), and the effects of hormonal contraceptives. Puberty onset was marked by a rise in fecal estradiol (fE2), followed by an elevation in CBT and circadian power. This time period marked the commencement of 4-day rhythmicity in fE2, CBT, and ultradian power marking the onset of the estrous cycle. The rise in circadian amplitude was accelerated by E2 treatment, indicating a role for this hormone in rhythmic development. Contraceptive administration in later adolescence reduced CBT and circadian power and resulted in disruption to 4-day cycles that persisted after discontinuation. Our data reveal with precise temporal resolution how biological rhythms change across adolescence and demonstrate a role for E2 in the emergence and preservation of multiscale rhythmicity. These findings also demonstrate how hormones delivered exogenously in a non-rhythmic pattern can disrupt rhythmic development. These data lay the groundwork for a future in which temperature metrics provide an inexpensive, convenient method for monitoring pubertal maturation and support the development of hormone therapies that better mimic and support human chronobiology.

Continuous Free Cortisol Profiles-Circadian Rhythms in Healthy Men

CONTEXT

The pituitary-adrenal axis had historically been considered a representative model for circadian rhythms. A recently developed portable collection device has provided the opportunity to evaluate free cortisol profiles using the microdialysis approach in individuals free to conduct their day-to-day activities in their own surroundings.

METHODS

Two separate experiments were conducted in healthy male volunteers. The total and subcutaneous (SC) free cortisol levels were measured at 10-minute intervals for a 24-hour period in one experiment, and the SC free cortisol levels were measured at 20-minute interval for 72 consecutive hours in free-living individuals in the second experiment.

RESULTS

The characteristic circadian rhythm was evident in both serum total and SC free cortisol, with the lowest levels achieved and maintained in the hours surrounding sleep onset and the peak levels occurring in every individual around waking. In all free-living individuals, the circadian rhythm was consistent across the 72-hour period, despite a wide range of activities. All the participants also showed increased cortisol after the consumption of lunch. The lowest levels during all 24-hour periods were observed during the hours after lights off, at the onset of sleep.

CONCLUSIONS

To the best of our knowledge, the present study is the first to report up to three consecutive 24-hour measurements of SC free cortisol in healthy individuals. We believe our study is a landmark study that paves the way for ambulatory monitoring of free cortisol profiles continuously for a period of 72 hours in free-living individuals performing their day-to-day activities whether healthy or with diseases involving the hypothalamic-pituitary-adrenal axis.

Improving glucocorticoid replacement profiles in adrenal insufficiency

There is an increased mortality associated with adrenal insufficiency despite glucocorticoid replacement therapy with a standardized mortality ratio greater than two. The cause of the increased mortality is yet to be definitively elucidated, but may be due to excess steroid exposure, or replacement regimens that are uncoupled from the normal physiological cortisol profile. Cortisol secretion follows an ultradian pattern which is not possible to reproduce using oral replacement. With the advent of new pumps, it is now possible to mimic the pulsatility of the adrenal glands. While the cognitive and emotional benefits of reproducing the ultradian rhythm are known, the presence of long-term benefits is not yet clear. There is a dearth of evidence and high-quality studies to underline our current understanding of the pathophysiology of adrenal insufficiency and replacement therapy. There is a particular lack of research comparing objective outcomes between patients receiving hydrocortisone replacement (either standard therapy or new sustained release preparations), prednisolone replacement and ultradian pumps. Direct comparative studies are now warranted to understand the optimal approach.

Mathematical Modelling of Endocrine Systems

Hormone rhythms are ubiquitous and essential to sustain normal physiological functions. Combined mathematical modelling and experimental approaches have shown that these rhythms result from regulatory processes occurring at multiple levels of organisation and require continuous dynamic equilibration, particularly in response to stimuli. We review how such an interdisciplinary approach has been successfully applied to unravel complex regulatory mechanisms in the metabolic, stress, and reproductive axes. We discuss how this strategy is likely to be instrumental for making progress in emerging areas such as chronobiology and network physiology. Ultimately, we envisage that the insight provided by mathematical models could lead to novel experimental tools able to continuously adapt parameters to gradual physiological changes and the design of clinical interventions to restore normal endocrine function.

Dysregulation of the hypothalamic pituitary adrenal (HPA) axis and cognitive capability at older ages: individual participant meta-analysis of five cohorts

Evidence on the association between functioning of the hypothalamic pituitary adrenal (HPA) axis and cognitive capability at older ages is mixed. We undertook a systematic review (until October 2016) and individual participant data (IPD) meta-analysis to test if dysregulation of the HPA axis is associated with worse cognitive capability. Five cohort studies were included in the IPD meta-analysis of diurnal cortisol patterns with crystallised and fluid cognitive ability. Higher night time cortisol was associated with worse fluid ability (standardised coefficient per SD increase −0.063, 95% CI −0.124, −0.002, P = 0.04; I² = 79.9%; age and gender adjusted). A larger diurnal drop was associated with better fluid ability (standardised coefficient per SD increase 0.037, 95% CI 0.008, 0.065, P = 0.01; I² = 49.2%; age and gender adjusted). A bigger cortisol awakening response (CAR) was weakly associated with better fluid (P = 0.09; I² = 0.0%; age and gender adjusted) and crystallised (P = 0.10; I² = 0.0%; age and gender adjusted) ability. There is weak evidence that a greater diurnal decline of the HPA axis and a larger CAR are associated with improvements in cognition at older ages. As associations are cross-sectional, we cannot rule out reverse causation.

Evidence for a Coupled Oscillator Model of Endocrine Ultradian Rhythms

Whereas long-period temporal structures in endocrine dynamics have been well studied, endocrine rhythms on the scale of hours are relatively unexplored. The study of these ultradian rhythms (URs) has remained nascent, in part, because a theoretical framework unifying ultradian patterns across systems has not been established. The present overview proposes a conceptual coupled oscillator network model of URs in which oscillating hormonal outputs, or nodes, are connected by edges representing the strength of node-node coupling. We propose that variable-strength coupling exists both within and across classic hormonal axes. Because coupled oscillators synchronize, such a model implies that changes across hormonal systems could be inferred by surveying accessible nodes in the network. This implication would at once simplify the study of URs and open new avenues of exploration into conditions affecting coupling. In support of this proposed framework, we review mammalian evidence for (1) URs of the gut-brain axis and the hypothalamo-pituitary-thyroid, -adrenal, and -gonadal axes, (2) UR coupling within and across these axes; and (3) the relation of these URs to body temperature. URs across these systems exhibit behavior broadly consistent with a coupled oscillator network, maintaining both consistent URs and coupling within and across axes. This model may aid the exploration of mammalian physiology at high temporal resolution and improve the understanding of endocrine system dynamics within individuals.

Ultradian rhythmicity of plasma cortisol is necessary for normal emotional and cognitive responses in man

Glucocorticoids (GCs) are secreted in an ultradian, pulsatile pattern that emerges from delays in the feedforward-feedback interaction between the anterior pituitary and adrenal glands. Dynamic oscillations of GCs are critical for normal cognitive and metabolic function in the rat and have been shown to modulate the pattern of GC-sensitive gene expression, modify synaptic activity, and maintain stress responsiveness. In man, current cortisol replacement therapy does not reproduce physiological hormone pulses and is associated with psychopathological symptoms, especially apathy and attenuated motivation in engaging with daily activities. In this work, we tested the hypothesis that the pattern of GC dynamics in the brain is of crucial importance for regulating cognitive and behavioral processes. We provide evidence that exactly the same dose of cortisol administered in different patterns alters the neural processing underlying the response to emotional stimulation, the accuracy in recognition and attentional bias toward/away from emotional faces, the quality of sleep, and the working memory performance of healthy male volunteers. These data indicate that the pattern of the GC rhythm differentially impacts human cognition and behavior under physiological, nonstressful conditions and has major implications for the improvement of cortisol replacement therapy.

Measuring cortisol in serum, urine and saliva - are our assays good enough?

Cortisol is a steroid hormone produced in response to stress. It is essential for maintaining health and wellbeing and leads to significant morbidity when deficient or present in excess. It is lipophilic and is transported bound to cortisol-binding globulin (CBG) and albumin; a small fraction (∼10%) of total serum cortisol is unbound and biologically active. Serum cortisol assays measure total cortisol and their results can be misleading in patients with altered serum protein concentrations. Automated immunoassays are used to measure cortisol but lack specificity and show significant inter-assay differences. Liquid chromatography - tandem mass spectrometry (LC-MS/MS) offers improved specificity and sensitivity; however, cortisol cut-offs used in the short Synacthen and Dexamethasone suppression tests are yet to be validated for these assays. Urine free cortisol is used to screen for Cushing's syndrome. Unbound cortisol is excreted unchanged in the urine and 24-h urine free cortisol correlates well with mean serum-free cortisol in conditions of cortisol excess. Urine free cortisol is measured predominantly by immunoassay or LC-MS/MS. Salivary cortisol also reflects changes in unbound serum cortisol and offers a reliable alternative to measuring free cortisol in serum. LC-MS/MS is the method of choice for measuring salivary cortisol; however, its use is limited by the lack of a single, validated reference range and poorly standardized assays. This review examines the methods available for measuring cortisol in serum, urine and saliva, explores cortisol in disease and considers the difficulties of measuring cortisol in acutely unwell patients and in neonates.

Transcription factor oscillations in neural stem cells: Implications for accurate control of gene expression

Naturally occurring oscillations in glucocorticoids induce a cyclic activation of the glucocorticoid receptor (GR), a well-characterized ligand-activated transcription factor. These cycles of GR activation/deactivation result in rapid GR exchange at genomic response elements and GR recycling through the chaperone machinery, ultimately generating pulses of GR-mediated transcriptional activity of target genes. In a recent article we have discussed the implications of circadian and high-frequency (ultradian) glucocorticoid oscillations for the dynamic control of gene expression in hippocampal neural stem/progenitor cells (NSPCs) (Fitzsimons et al., Front. Neuroendocrinol., 2016). Interestingly, this oscillatory transcriptional activity is common to other transcription factors, many of which regulate key biological functions in NSPCs, such as NF-kB, p53, Wnt and Notch. Here, we discuss the oscillatory behavior of these transcription factors, their role in a biologically accurate target regulation and the potential importance for a dynamic control of transcription activity and gene expression in NSPCs.

Effect of a pre-exercise hydrocortisone dose on short-term physical performance in female patients with primary adrenal failure

OBJECTIVE

Many patients with primary adrenal insufficiency (Addison's disease) take extra doses of glucocorticoids during stressful events, but a benefit has not been demonstrated in controlled trials. Here, we investigated the effects of a pre-exercise hydrocortisone dose on cardiorespiratory, hormonal and metabolic parameters in response to short-term strenuous physical activity.

DESIGN

This was a randomized placebo-controlled, two-week cross-over clinical trial.

PARTICIPANTS

Ten women with Addison's disease and 10 age-matched healthy females participated in the study.

MEASUREMENTS

All women in the study underwent maximal incremental exercise testing. A stress dose of 10 mg hydrocortisone or placebo was given 1 h prior to exercise on two occasions. Blood samples were drawn before, and 0, 15 and 30 min post exercise. Oxygen uptake, maximal aerobic capacity, endocrine and metabolic responses to physical activity, as well as health status by questionnaires were evaluated.

RESULTS

Maximal aerobic capacity and duration of exercise were significantly lower in patients than in healthy subjects and did not improve with the treatment. After an extra hydrocortisone dose serum cortisol was significantly higher than in the healthy subjects (P<0.001). Post-exercise glucose and adrenaline levels were significantly lower and free fatty acids insignificantly higher in patients irrespective of stress dose. Stress dosing did not alter other metabolic or hormonal parameters or quality of life after the exercise.

CONCLUSIONS

The patients did not benefit from an extra dose of hydrocortisone in short strenuous exercise. Stress dosing may not be justified in this setting. Whether stress dosing is beneficial in other types of physical activity will have to be examined further.

Rapid intra-adrenal feedback regulation of glucocorticoid synthesis

The hypothalamic–pituitary–adrenal axis is a vital neuroendocrine system that regulates the secretion of glucocorticoid hormones from the adrenal glands. This system is characterized by a dynamic ultradian hormonal oscillation, and in addition is highly responsive to stressful stimuli. We have recently shown that a primary mechanism generating this ultradian rhythm is a systems-level interaction where adrenocorticotrophin hormone (ACTH) released from the pituitary stimulates the secretion of adrenal glucocorticoids, which in turn feedback at the level of the pituitary to rapidly inhibit ACTH secretion. In this study, we combine experimental physiology and mathematical modelling to investigate intra-adrenal mechanisms regulating glucocorticoid synthesis. Our modelling results suggest that glucocorticoids can inhibit their own synthesis through a very rapid (within minutes), presumably non-genomic, intra-adrenal pathway. We present further evidence for the existence of a short time delay in this intra-adrenal inhibition, and also that at the initiation of each ACTH stimulus, this local feedback mechanism is rapidly antagonized, presumably via activation of the specific ACTH receptor (MC2R) signalling pathway. This mechanism of intra-adrenal inhibition enables the gland to rapidly release glucocorticoids while at the same time preventing uncontrolled release of glucocorticoids in response to large surges in ACTH associated with stress.

A phase 2 study of Chronocort, a modified-release formulation of hydrocortisone, in the treatment of adults with classic congenital adrenal hyperplasia

CONTEXT

Treatment of congenital adrenal hyperplasia (CAH) is suboptimal. Inadequate suppression of androgens and glucocorticoid excess are common and current glucocorticoid formulations cannot replace the cortisol circadian rhythm.

OBJECTIVES

The primary objective was to characterize the pharmacokinetic profile of Chronocort, a modified-release hydrocortisone formulation, in adults with CAH. Secondary objectives included examining disease control following 6 months of Chronocort with dose titration.

DESIGN, SETTING, AND PATIENTS

Sixteen adults (eight females) with classic CAH participated in an open-label, nonrandomized, Phase 2 study at the National Institutes of Health Clinical Center. Twenty-four-hour blood sampling was performed on conventional glucocorticoids and following 6 months of Chronocort. Chronocort was initiated at 10 mg (0700 h) and 20 mg (2300 h). Dose titration was performed based on androstenedione and 17-hydroxyprogresterone (17-OHP) levels and clinical symptomatology.

MAIN OUTCOME MEASURES

The primary outcome was cortisol pharmacokinetics of Chronocort and secondary outcomes included biomarkers of CAH control (androstenedione and 17-OHP).

RESULTS

In patients with CAH, Chronocort cortisol profiles were similar to physiologic cortisol secretion. Compared with conventional therapy, 6 months of Chronocort resulted in a decrease in hydrocortisone dose equivalent (28 ± 11.8 vs 25.9 ± 7.1 mg/d), with lower 24-hour (P = .004), morning (0700-1500 h; P = .002), and afternoon (1500-2300 h; P = .011) androstenedione area under the curve (AUC) and lower 24-hour (P = .023) and morning (0700-1500 h; P = .02) 17-OHP AUC.

CONCLUSIONS

Twice-daily Chronocort approximates physiologic cortisol secretion, and was well tolerated and effective in controlling androgen excess in adults with CAH. This novel hydrocortisone formulation represents a new treatment approach for patients with CAH.

Subcutaneous pulsatile glucocorticoid replacement therapy

The glucocorticoid hormone cortisol is released in pulses resulting in a complex and dynamic ultradian rhythm of plasma cortisol that underlies the classical circadian rhythm. These oscillating levels are also seen at the level of tissues such as the brain and trigger pulses of gene activation and downstream signalling. Different patterns of glucocorticoid presentation (constant vs pulsatile) result not only in different patterns of gene regulation but also in different neuroendocrine and behavioural responses. Current 'optimal' glucocorticoid replacement therapy results in smooth hormone blood levels and does not replicate physiological pulsatile cortisol secretion. Validation of a novel portable pulsatile continuous subcutaneous delivery system in healthy volunteers under dexamethasone and metyrapone suppression. Pulsatile subcutaneous hydrocortisone more closely replicates physiological circadian and ultradian rhythmicity.