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Topic:Adrenal
The adrenal glands in horses are small endocrine organs located near the kidneys, responsible for producing a variety of hormones essential for physiological regulation. These hormones include cortisol, adrenaline, and aldosterone, which are involved in stress response, metabolism, and electrolyte balance. The functioning of the adrenal glands is integral to the horse's ability to respond to stressors and maintain homeostasis. Research in equine endocrinology often focuses on understanding the regulation of adrenal hormones, their role in equine health, and the impact of disorders such as equine Cushing's disease and adrenal insufficiency. This page compiles peer-reviewed research studies and scholarly articles that explore the anatomy, function, and clinical implications of adrenal gland activity in horses.
Training- and competition-related changes on circulating adrenocorticotropic hormone and cortisol response in Thoroughbred Racehorses. Exercise is a physiological challenge inducing intensity-dependent hypothalamic-pituitary-adrenal (HPA) axis responses. The hypothesis was that training and racing sessions induce different HPA axis activation. Objective: To assess whether different exercise sessions affect equine adrenal responsiveness according to age and sex. Methods: Ten clinically healthy Thoroughbred racehorses (6 females and 4 males) were recruited. Four were 2 years old and six were 3 years old. Horses were subjected to two exercise conditions: training and competitive racing sessions. Blood samples were collected at r...
Hypothalamic-pituitary-adrenal axis response and glucose homeostasis during exercise to fatigue before and after training in old and young adult Standardbred mares. While reduced cortisol responses to exercise have been described in older horses, the effects of aging and training on the hypothalamic-pituitary-adrenal axis (HPA axis) and downstream metabolic signaling are currently unknown. Unassigned: This study tested the hypothesis that age and exercise training alter the response of the HPA axis, insulin, and glucose during an acute exercise challenge to fatigue. Methods: Six old (22.0±0.7 years) and six young adult (7.3±0.6 years) unfit Standardbred mares were tested. Mares ran a graded exercise test before (GXT1) and after (GXT2) 8 weeks of trainin...
Vasopressin stimulation testing in hospitalized foals. Hypothalamic-pituitary-adrenal gland axis (HPAA) dysfunction impairs survival and can be diagnosed with an arginine vasopressin (AVP) stimulation test. Objective: Adrenocorticotropic hormone (ACTH) and cortisol response to an AVP stimulation test will be attenuated in hospitalized foals compared to healthy foals and associated with severity of disease. Methods: Fifteen healthy and 45 hospitalized foals: 19 septic, 26 sick non-septic (SNS). Methods: A prospective, observational case-control design was utilized to assess HPAA function and compare corticotropin-releasing hormone, ACTH, and cortis...
Comparison of in vitro degradation of immunoreactive adrenocorticotropic hormone and insulin in equine blood measured by two immunoassay methods. This study compared the in vitro stability of equine plasma adrenocorticotrophic hormone (ACTH) and serum insulin measured by chemiluminescent assay (CLA; Siemens Immulite 2000XPi) and immunofluorescent assay (IFA; Tosoh AIA-900) after storage at 4°C or room temperature (approximately 21°C) for clinically relevant periods. Fresh equine EDTA blood for ACTH and coagulated blood for insulin were aliquoted and analysed immediately (T0) and after storage. ACTH was assessed at 24, 48 and 72 hours; insulin was assessed at 24 hours, 72 hours and 7 days. Percentage recovery relative to T0 was analyse...
Transference of diagnostic thresholds for equine plasma ACTH from the Immulite 1000 to Immulite 2000XPi and Tosoh AIA systems. Diagnosis of PPID in horses relies on measurement of plasma adrenocorticotrophic hormone (ACTH) concentrations. Because measured ACTH values vary between analytical platforms, and published diagnostic thresholds apply almost exclusively to the Immulite 1000 chemiluminescent assay (CLA), there is a need for validated, assay-specific thresholds for contemporary analysers. This study aimed to transfer and validate established Immulite 1000 diagnostic thresholds for plasma ACTH to three contemporary systems (Immulite 2000XPi, Tosoh AIA-900, and Tosoh AIA-360) using the Clinical Laboratory Standard...
Adrenocorticotropic Hormone and Thyroxine Concentrations in Young Healthy Equids: Species Differences and Seasonal Variations. Due to growing interest in endocrine diseases, more studies aim to interpret the baseline concentrations and reference intervals of hormone values like adrenocorticotropic hormone (ACTH) and thyroxine (T4) in horses. Most studies available in the literature focus on evaluating ACTH and thyroid hormone values in adult and geriatric horses, with only a few considering younger donkeys and ponies. This study aimed to measure ACTH and T4 in autumn and spring in younger equids. The study included 42 young equids, which were divided into three groups: horses, ponies, and donkeys. The concentration of...
Assessment of baseline adrenocorticotropic hormone and insulin concentrations in healthy horses in Saskatchewan over a 1-year period. Endocrine disorders in horses, such as pituitary pars intermedia dysfunction and equine metabolic syndrome, rely on hormone testing for diagnosis, but seasonal and regional variabilities highlight the need for locally generated data. Objective: To characterize monthly blood concentrations of ACTH and insulin over 1 year in healthy horses in Saskatchewan. A secondary objective was to assess the association between these outcomes and the following factors: sex, age, breed, pregnancy status, level of exercise, body condition score, and cresty neck score. Methods: Sixty-eight clinically healthy, c...
Serum cortisol concentrations in newborn foals are increased by transfusion with anti-rhodococcal hyperimmune plasma and inversely associated with immunoglobulin activity. Transfusion of Rhodococcus equi hyperimmune plasma (REHIP) to neonatal foals is done to reduce the incidence of rhodococcal pneumonia. Objective: To determine effects in newborn foals of REHIP transfusion on serum cortisol concentrations; the association of serum cortisol concentrations with serum globulin concentration and anti-rhodococcal immunoglobulin activity; and cumulative incidence of rhodococcal pneumonia. Methods: Serum samples were collected from 356 newborn foals from 13 New York farms immediately before and after transfusion of 1 L or 2 L of REHIP. Serum samples were assayed for c...
Exploring the association between stress-related hormonal changes, behaviours and facial movements after an interval training exercise in French Standardbred. Physical exercise can act as a physiological and a mental stressor. Monitoring exercise-induced stress is therefore essential to understand racehorses 'responses to effort and to ensure their welfare. Stress perceived by the horse during physical activity can be measured using various indicators, including stress-related hormones such as cortisol and adrenaline, and other neuromodulators such as serotonin, all involved in the stress response and its regulation. Another approach to assess physiological and emotional responses to stimuli such as exercise is through behaviours and facial movement...
Seasonal elevation in equine adrenocorticotropic hormone occurs throughout the contiguous United States and is influenced by latitude and age. To determine whether seasonal variation in equine plasma ACTH concentrations is affected by latitude between 29.7°N and 45.0°N in the US. Unassigned: A cohort study was performed between June 2019 and May 2020 in which plasma ACTH was measured monthly by chemiluminescence immunoassay. The study involved 201 apparently healthy horses from 9 locations within the US classified into northern, central, and southern latitude cohorts. Data analysis was performed with 3 major objectives: (1) identify outlier ACTH concentrations and horses; (2) estimate ACTH upper reference limits to define expected ...
Investigation of peptide cross reactivity in equine plasma using two adrenocorticotropic hormone immunoassays. This study aimed to further define and quantify possible cross-reactive peptides when measuring plasma adrenocorticotropic hormone (ACTH) concentration in equids. Equine plasma samples were spiked with known concentrations of exogenous manufactured peptides comprising human ACTH, ACTH (corticotropin-like intermediate lobe peptide, CLIP) and ACTH (corticotropin inhibiting peptide, CIP). All samples were assayed in duplicate using Siemens Immulite 2000xpi chemiluminescent assay (CLA) and Tosoh AIA-900 immunoflurorescent assay (IFA). As expected, ACTH was measured by both assays although higher v...
Overnight dexamethasone suppression and cortisol index tests in clinically healthy horses and with crib-biting. The dexamethasone suppression test (DST) has been used in humans for the diagnosis of psychiatric problems such as depression, anxiety and Cushing's syndrome, and in horses for the ante mortem diagnosis of dysfunction of the intermediate part of the pituitary. Objective: This study aimed to examine the functionality of the hypothalamic-pituitary-adrenal axis through the DST and the cortisol index (CI), to evaluate the rhythmicity of the circadian cycle of cortisol in healthy horses with crib-biting or windsucking. Methods: A total of 20 Colombian Creole horses of both sexes, under similar mana...
Circulating ACTH and Cortisol Investigations in Standardbred Racehorses Under Training and Racing Sessions. The hypothalamic-pituitary-adrenal (HPA) axis is a neuroendocrine system involved in the coping response to stressful challenges during exercise stimuli. Exercise represents a significant disruptor of homeostasis, inducing an ACTH-cortisol co-secretion, based on different characteristics of exercise in sport horses. Based on this statement, the aim of this study is to evaluate the circulating adrenocorticotropin and cortisol changes in Standardbred trotters, after training and racing sessions, considering the different age and sex. In particular, the aim is to determine to what extent the leve...
Endogenous Nature of Hydrocortisone Acetate in Horse. Hydrocortisone acetate, a synthetic acetate ester of hydrocortisone, was detected in horse blood samples collected from Thoroughbreds. Hydrocortisone acetate is generally considered an indicator for exogenous administration in horses. As hydrocortisone acetate has been previously reported to be endogenous in selected mammals, a proof-of-concept study was performed to evaluate the possible endogenous nature of hydrocortisone acetate in horses by in vitro incubation experiments using homogenized horse brain tissue.
Collecting equine whole blood in glass tubes does not decrease adrenocorticotropic hormone concentration compared to plastic tubes. Pituitary pars intermedia dysfunction is diagnosed using immunoreactive ACTH concentrations. Glass reportedly binds ACTH, but the clinical relevance of using glass blood tubes for measuring equine ACTH concentrations is controversial. This study investigates whether the collection of whole blood into glass EDTA tubes and storage for up to 6 hours changes ACTH concentrations compared to plastic EDTA tubes. Unassigned: This was a cohort study. Whole blood was collected into both glass and plastic EDTA tubes from 9 horses > 12 years of age, including 4 with pituitary pars intermedia dysfunctio...
Association Between Adrenocorticotropic Hormone Concentration and Clinical Signs of Pituitary Pars Intermedia Dysfunction in Swiss and Austrian Equids. There remains a scarcity of data concerning the relationship between the clinical signs associated with PPID and plasma ACTH concentrations. Objective: Report the frequency of clinical signs in the study cohort and identify individual clinical signs or combinations of clinical signs associated with high ACTH concentrations. Methods: Two hundred eighty equids were examined by private veterinarians. Methods: A cross-sectional study of animals with clinical suspicion of PPID was conducted between August and November. Private practitioners completed an online questionnaire reporting detailed infor...
Meta-Analysis and Mechanism-Based Modeling of Synovial and Plasma Pharmacokinetics and Adrenal Suppression Following Intra-Articular Injection of Methylprednisolone Acetate in Horses. This study assesses the pharmacokinetics (PK) of published methylprednisolone (MPL) data in horses following intra-articular (IA) administration of MPL acetate (MPA) and the associated adrenal suppression. The concentrations of MPL/MPA in synovial fluid, blood, and urine, as well as hydrocortisone (HC) in plasma, were digitized from multiple sources in the literature. A minimal physiologically based pharmacokinetic model and a linked indirect response model with a circadian rhythm baseline were applied. Concentrations of MPA in joints followed a triexponential decay, converting to MPL. The cle...
Renin-Angiotensin-Aldosterone System Profiling in Horses Before and After Exercise. The impact of exercise on the classical and alternative renin-angiotensin-aldosterone system (RAAS) pathways has not been studied in horses. Objective: We hypothesized that exercise would activate both RAAS pathways and that endurance exercise would cause more activation of the classical pathway compared to short-duration, high-intensity exercise in horses. Methods: Twenty-five horses (21 client-owned and 4 research) were included in 4 exercise groups (10 Arabians, 50-mile ride [A-E]; 4 thoroughbreds, 1-mile treadmill exercise [TB-TM]; 5 thoroughbreds, 1-1/16th-mile race [TB-R]; and 6 quarter ...
The Effect of Season and Breed on Hypothalamic-Pituitary-Adrenal Axis Hormones, Metabolic Hormones, and Oxidative Markers in Ponies and Horses. Endocrine function in ponies differs from horses, with seasonally increased concentrations of plasma adrenocorticotropic hormone (ACTH) and an increased risk of insulin dysregulation. Objective: (1) Season and breed differences exist in concentrations of hypothalamic-pituitary-adrenal axis and metabolic hormones; and (2) systemic oxidative status is significantly different between ponies and horses and correlates with endocrine hormones. Methods: Thirty-four healthy Welsh ponies and 14 healthy Quarter horses. Methods: Blood was collected from Welsh ponies and Quarter horses in the same region ...
Time but not storage of equine plasma in silicate-coated tubes affects adrenocorticotropic hormone stability. Pituitary pars intermedia dysfunction (PPID) is diagnosed by measuring the ACTH concentrations. Due to the reported instability of ACTH, it is recommended to transfer centrifuged plasma into cryovials; however, in practice, cryovials are infrequently used, and serum (red-top) tubes are used instead. This study investigated whether this procedure affects ACTH concentrations and the diagnosis of PPID. Unassigned: This was a cohort study. Blood was collected into EDTA tubes from 9 horses with PPID and 7 controls. After centrifugation, plasma was either aliquoted into a cryovial or into a serum tu...
Distribution and sequence analysis of the melanocortin 2 receptor in horses and ponies. The melanocortin 2 receptor (MC2R) has relevance to equine pituitary pars intermedia dysfunction (PPID), as it is the primary binding site for ACTH, which circulates at elevated concentrations in animals affected by PPID. Despite this, little is known about MC2R in equine species. The overall aim of this investigation was to determine MC2R mRNA expression in tissues relevant to PPID in healthy horses and to examine the MC2R gene sequence in a cohort of horses and ponies with and without PPID. The study found that the MC2R gene was expressed in both adrenal and pituitary gland tissues as report...
Effect of age on amplitude of circulating catecholamine’s change of healthy cyclic mares. Catecholamines (CATs) are neurotransmitters and allostatic hormones whose plasma concentrations are physiologically modified in various species such as human, rats, mice and donkeys, with advancing age. However, currently these mechanisms are less well elucidated in horses and more specifically in mares. The hypothesis of this study was that, as in afore mentioned species, the CATs could experience physiological changes with advancing age. The objective of this study was to evaluate the concentrations of adrenaline (A), noradrenaline (NA), dopamine (DA), and serotonin (5-HT) in mares of differ...
Effect of age on androgens pattern in cyclic mares. Androgens are produced in both sexes. In females produced by the adrenal gland and the ovaries they play a crucial role in regulating ovarian function, estrogen synthesis and follicular growth. Age leads to a reduction in androgen concentrations, although, at present, these mechanisms are not elucidated in mares. The objective of this study was to evaluate the concentrations of testosterone (T), androstenedione (A) and dehydroepiandrosterone (DHEA) in mares of different ages. Blood samples were drawn from seventy cyclic Spanish Purebred mares belonging to five age groups: 3-5 years, 6-9 year...
Detection of doping peptides and basic drugs in equine urine using liquid chromatography-mass spectrometry. The abuse of prohibited agents including peptides and basic small-molecule drugs is an area of great concern in horseracing due to their high potential to act as doping agents. These compound classes include agents such as growth hormone-releasing peptides, peptide analgesics, beta-2-adrenergic receptor agonists, and quaternary ammonium drugs that can be challenging to detect and regulate because of their chemical properties and potential rapid elimination following administration. The use of highly sensitive and selective analytical techniques such as liquid chromatography-mass spectrometry (...
Assessment of the hypothalamic-pituitary-adrenocortical axis function using a vasopressin stimulation test in neonatal foals. Bacterial sepsis is the leading cause of death in foals and is associated with hypothalamic-pituitary-adrenocortical axis (HPAA) dysfunction. HPAA function can be evaluated by an arginine-vasopressin (AVP) stimulation test. Objective: Administration of AVP will stimulate a dose-dependent rise in systemic adrenocorticotropin-releasing hormone (ACTH) and cortisol in neonatal foals. There will be no response seen in corticotropin-releasing hormone (CRH) and baseline AVP will be within reference interval. Methods: Twelve neonatal foals, <72 hours old. Methods: HPAA function was assessed in fo...
Evaluation of the effect of glucocorticoid treatment on adrenocortical functions by monitoring endogenous hydrocortisone in horses. Glucocorticoid preparations have anti-inflammatory effects, and are commonly used in the equine clinical setting; however, such treatments can cause a number of side effects. Adrenal insufficiency is an adverse effect induced by the suppression of adrenal function following drug administration. This study aimed to investigate the influence of two glucocorticoid preparations, dexamethasone and hydrocortisone, on adrenocortical function in horses. The usual doses of dexamethasone and hydrocortisone preparations in equine practice were administered intramuscularly to six horses, and peripheral bl...
Successful surgical removal of a pheochromocytoma in a mare via trans-costal approach. Pheochromocytomas have been previously reported in horses, but successful antemortem diagnosis and surgical removal without recurrence of clinical signs have not been described. Objective: To report the clinical presentation, diagnostic evaluation, surgical technique, anaesthetic management and post-operative care of a mare diagnosed with pheochromocytoma. Methods: Clinical case report. Methods: An 18-year-old Quarter Horse mare presented for recurrent episodes of colic, profuse sweating, muscle fasciculations and agitation over a 2-month period. Clinical, clinicopathologic and ultrasonographi...
The hypothalamic-pituitary-adrenal axis response to ovine corticotropin-releasing-hormone stimulation tests in healthy and hospitalized foals. The hypothalamic-pituitary-adrenocortical axis (HPAA) response to sepsis can be impaired in critical illness. Corticotropin-releasing hormone (CRH) stimulation test might assess HPAA function in foals. Objective: To evaluate plasma cortisol, ACTH, arginine vasopressin (AVP), and endogenous CRH (eCRH) response to different doses of ovine CRH (oCRH). Methods: Healthy (n = 14) and hospitalized (n = 15) foals <7 days of age. Methods: In this prospective randomized study, oCRH (0.1, 0.3, and 1 μg/kg) was administered intravenously and blood samples were collected before, 15, 30, 60, and ...
Longitudinal assessment of adrenocortical steroid and steroid precursor response to illness in hospitalized foals. Sepsis is a major cause of morbidity and mortality in neonatal foals. Relative adrenal insufficiency (RAI), defined as an inadequate cortisol response to stress, has been associated with sepsis, prematurity, and poor outcome in newborn foals. In addition to cortisol, the adrenal gland synthesizes several biologically important steroids and steroid precursors, including aldosterone, androgens, and progestogens. However, concentration of these hormones during hospitalization and their association with the severity of disease and mortality in critically ill foals have not been completely evaluate...
