Topic:Cortisol
Cortisol is a steroid hormone produced by the adrenal glands in horses, playing a significant role in the regulation of metabolism, immune response, and stress management. As a glucocorticoid, cortisol influences various physiological processes, including glucose metabolism, inflammation modulation, and the maintenance of homeostasis during stress. Its levels in horses can vary due to factors such as exercise, environmental changes, and psychological stressors. Cortisol is often measured to assess stress responses and overall well-being in equine health management. This page compiles peer-reviewed research studies and scholarly articles that explore the production, regulation, and implications of cortisol in equine physiology and health.
Different approaches to the identification of a cortisol isomer compound in horse urine. A threshold concentration for cortisol in equine urine was fixed at 1.0 microgram ml-1 by the racing authorities in 1994. In some circumstances, interlaboratory discrepancies were observed and structural cortisol modification was revealed. In order to elucidate the degradation process and to prevent it, an identification study of the produced compound was carried out. The modified substrate was characterised by the same molecular weight as cortisol and a shorter retention time under the conditions used for the cortisol quantification (M.A. Popot, PhD Thesis, King's College, London, 1996). To i...
The effects of intrafetal ACTH administration on the outcome of pregnancy in the mare. Enhanced adrenocortical activity in the fetus is related to the onset of parturition in many species. The aim of this study was to determine the effect of injection of fetal ACTH on gestational length and fetal viability in the horse. Pony mares (n=23) were studied from 300 days gestation. Seven control mares (Group 1) received three consecutive intrafetal injections of sterile water, while fetuses of a further 16 mares received Depot ACTH1-24. These mares were either allowed to foal spontaneously (Group 2, n=4) or delivery was induced within 3 days of the last fetal injection (Group 3, n=7); ...
Effect of exercise on the immune response of young and old horses. To compare exercise-induced immune modulation in young and older horses. Methods: 6 young and 6 aged horses that were vaccinated against equine influenza virus. Methods: Venous blood samples were collected for immunologic assessment before and immediately after exercise at targeted heart rates and after exercise for determination of plasma lactate and cortisol concentrations. Mononuclear cells were assayed for lymphoproliferative responses and incubated with interleukin-2 (IL-2) to induce lymphokine-activated killer (LAK) cells. Antibodies to equine influenza virus were measured. Results: Olde...
Perioperative plasma cortisol concentration in the horse. The cortisol response to anaesthesia and surgery was studied in 2 groups of horses undergoing either abdominal or non-abdominal surgery. The preoperative mean plasma cortisol concentration (pcc) of 381.7 nmol/l (s.d. 254.7) was markedly higher in the abdominal group than the early-morning mean pcc of 115.6 nmol/l (s.d. 78.4) in the non-abdominal group. During halothane anaesthesia and surgery the mean pcc increased significantly (p < 0.05) from the preoperative mean of 119.2 to 215.9 nmol/l (s.d. 79.8) after 30 min of surgery in the non-abdominal group. In the abdominal group a decrease occ...
Effects of hypoxia on endocrine and metabolic responses to anaesthesia in ponies. Some metabolic and endocrine effects of hypoxaemia were studied during halothane anaesthesia in six ponies. Each was anaesthetised twice; on one occasion a 20-minute period of hypoxaemia (arterial oxygen tension between 4.4 and 5.8 [mean 5.3] kPa) was imposed during 120 minutes of anaesthesia. On the second occasion arterial oxygen tension was maintained above 17 kPa throughout. Routine cardiovascular monitoring was performed and blood samples were taken to measure haematocrit, cortisol, insulin, glucose and lactate. Anaesthesia was associated with hypotension in both groups (mean ABP 7.0 kPa...
Diurnal variation and age differences in the biochemical markers of bone turnover in horses. Biochemical markers of bone turnover provide sensitive, rapid, and noninvasive monitoring of bone resorption and formation. Serum concentrations of osteocalcin (OC) reflect rates of bone formation, and urinary concentrations of the pyridinium crosslinks pyridinoline (Pyd) and deoxypyridinoline (Dpd) are specific and sensitive markers of bone resorption. These markers are age-dependent and are used to detect and monitor changes in the rates of bone turnover in a variety of orthopedic diseases in humans and may prove to have similar application in horses. This study examined age differences and ...
Endocrine and metabolic responses to plasma volume expansion during halothane anesthesia in ponies. The study was designed to contribute to identification of the stimulus to adrenocortical activity during halothane anaesthesia in equidae. Two groups of six ponies were premedicated with acepromazine before induction of anaesthesia with thiopentone and maintenance for 120 min with halothane in oxygen. In group H Haemaccel modified gelatine plasma replacer was infused (48+/-13 mL/kg) to maintain mean arterial blood pressure (MABP) close to preanaesthetic values. In group DH, blood pressure was maintained close to preanaesthetic levels with a lower dose of Haemaccel (10 mL/kg) combined with an i...
Pituitary-adrenocortical effects of methoxamine infusion on halothane anaesthetised ponies. This study investigated whether maintenance of normotension using a methoxamine infusion would prevent activation of the stress response during halothane anaesthesia in ponies. After acepromazine premedication, anaesthesia was induced with thiopentone in six ponies, and maintained for 120 minutes with halothane in oxygen and ventilation to normocapnia. Methoxamine (M, 0.013+/-0.005 mg kg(-1) min(-1)) or saline (C) was infused throughout anaesthesia. Sequential blood samples were taken for cortisol and ACTH assay. During anaesthesia normotension (mean arterial blood pressure 101-124 mm Hg) was ...
Physiological and behavioral consequences associated with short-term prevention of crib-biting in horses. Crib-biting in the horse is frequently prevented in the short-term by horse-owners using physical means. Because it has been proposed that crib-biting may function to reduce stress, the effect of prevention of crib-biting and/or eating on the behaviour, heart rate, and plasma cortisol and beta-endorphin concentrations was measured in six crib-biting and six normal horses. When crib-biters were unable to crib-bite, they showed an increase in ingestive behaviour. When crib-biters were prevented from crib-biting and eating, a relative stasis in the motility of the foregut occurred, suggesting tha...
Effects of differently composed feeds and physical stress on plasma gastrin concentration in horses. Plasma gastrin concentrations were determined in 6 Standardbreds (4 geldings and 2 mares) after 3 different meals consisting of unlimited amounts of hay (8-9 kg per horse), a restricted amount of hay (0.6 kg/100 kg body-weight) and grain (0.2 kg/100 kg body-weight) in combination or of grain alone (0.2 kg/100 kg body-weight). In another series of experiments the possible role of gastrin as a stress hormone was investigated. Plasma gastrin and cortisol concentrations were determined during fasting and compared with concentrations during hay feeding. In addition, gastrin and cortisol concentrati...
Effects of hypercapnia on endocrine and metabolic responses to anaesthesia in ponies. Some metabolic and endocrine effects of hypercapnia were studied in six ponies during halothane anaesthesia with neuromuscular blockade and controlled ventilation. Each was anaesthetised twice, once with a 40-minute-period of hypercapnia (10 kPa) and once when normocapnia (5.3 kPa) was maintained throughout two hour's anaesthesia. Routine cardiovascular monitoring was performed and blood samples were taken for assay of cortisol, insulin, glucose, lactate, muscle and liver enzymes and total protein. Anaesthesia induced hypotension and lacticacidaemia which were slightly ameliorated during hyper...
Adrenocortical and metabolic responses to dobutamine infusion during halothane anaesthesia in ponies. The study investigated whether hypotension in halothane-anaesthetised ponies is the stimulus inducing an endocrine stress response by assessing the effect of maintenance of normotension with a dobutamine infusion. Groups of six ponies were studied. After premedication with acepromazine (0.04 mg/kg) anaesthesia was induced with thiopentone (10 mg/kg) and maintained for 120 min with halothane (group AN). Dobutamine was infused to effect (1.1-4.4 microg/kg/min) to maintain arterial pressure at pre anaesthetic levels. The conscious group (CON) were prepared as for AN and then received only dobutam...
Alteration in adrenocortical function in horses with recurrent airway obstruction after aerosol and parenteral administration of beclomethasone dipropionate and dexamethasone, respectively. To determine alteration in adrenocortical function in horses with recurrent airway obstruction (heaves) after aerosol and parenteral administration of beclomethasone dipropionate and dexamethasone, respectively. Methods: 6 horses with inducible and reversible heaves. Methods: Episodes of heaves were induced by exposure to moldy hay and straw for 7 days (natural challenge). Horses then underwent treatment (aerosolized beclomethasone, parenterally administered dexamethasone, and aerosolized propellant) for 7 days. Horses remained in the mold-contaminated environment for 7 days after discontinuat...
Cardiovascular effects of surgical castration during anaesthesia maintained with halothane or infusion of detomidine, ketamine and guaifenesin in ponies. Sixteen colts were premedicated with acepromazine and anaesthesia was induced with detomidine and ketamine. Ponies were randomly allocated to receive halothane (HAL) or infusion of detomidine, ketamine and guaiphenesin (DKG) to maintain anaesthesia. Heart and respiratory rate, ECG, mean arterial blood pressure (MABP), cardiac index (CI), blood gases and plasma cortisol, ketamine and guaiphenesin were measured. Surgical castration took place between 45 and 75 min and anaesthesia lasted 90 min. MABP with DKG was significantly higher than with HAL, and, with HAL, MABP increased from pre-surgery (...
The effect of social stress on adrenal axis activity in horses: the importance of monitoring corticosteroid-binding globulin capacity. Plasma cortisol is largely bound to corticosteroid-binding globulin (CBG), which regulates its bioavailability by restricting exit from capillaries. Levels of CBG may be altered by several factors including stress and this can influence the amount of cortisol reaching cells. This study investigated the effect of social instability on plasma concentrations of CBG, total and free (not protein bound) cortisol in horses. Horses new to our research herd ('newcomers') were confined in a small yard with four dominant resident horses for 3-4 h daily for 3-4 (n = 5) or 9-14 (n = 3) days. Jugular blood ...
[Equine Cushing syndrome (ECS). Case report, review of its diagnosis and therapy and substantial differences from Cushing syndrome in dogs]. Equine and canine Cushing's syndrome, both of which are the result of elevated cortisol levels, show some different pathogenetical and clinical features and require different therapeutical approaches. In older horses the equine Cushing's syndrome (ECS) is not uncommon. Nearly all cases result from excessive hormone production in cells of the pars intermedia of the pituitary. Besides elevated levels of adrenocorticotrope hormone (ACTH), high peripheral levels of pro-opiomelanocortin, beta-endorphines and alpha-melanocyte-stimulating hormone can be measured. In middle-aged and geriatric dogs, Cu...
Effects of surgery on endocrine and metabolic responses to anaesthesia in horses and ponies. The effects of surgery on endocrine and metabolic responses to anaesthesia were investigated in seven horses and eight ponies. They were anaesthetised twice and surgery was carried out on one occasion. Cardiorespiratory monitoring was performed and blood samples were taken for assay of cortisol, glucose, lactate, insulin, catecholamines and non-esterified fatty acids. All groups developed arterial hypotension which was more marked in the surgical groups where post operative pulse rate was also higher. Plasma cortisol concentration increased in all groups during anaesthesia but remained higher ...
Adrenal insufficiency in a neonatal foal. A 3-day-old female Pinto was admitted with profuse watery diarrhea and severe hypovolemic shock. After 1 week of intensive care, the foal developed seizures associated with profound serum electrolyte abnormalities suggestive of hypoadrenocorticism. Treatment with prednisone and isotonic saline (0.9% NaCl) solution led to prompt clinical response. Premature withdrawal of prednisone resulted in relapse of clinical signs. A diagnosis of adrenal insufficiency was made on the basis of clinical signs, electrolyte abnormalities, low baseline cortisol concentration, and lack of response to administrat...
Catecholamine and cortisol responses of horses to incremental exertion. The responses of the plasma concentrations of catecholamines and cortisol in horses to varied relative intensities of exertion were examined. The plasma concentrations of cortisol, epinephrine and norepinephrine increased significantly (p < 0.05) with exertion. The plasma cortisol concentrations at relative work intensities of 48.3% +/- 1.4%, 82.3% +/- 2.0% and 99.6% +/- 0.4% of VO2max were 114%, 124%, and 126%, respectively, of those at rest, whereas the plasma epinephrine concentrations were 239%, 772% and 3483%, and the norepinephrine concentrations were 138%, 255%, and 1121% of the valu...
Cortisol, peptides and catecholamines in cerebrospinal fluid, pituitary effluent and peripheral blood of ponies. Cannulation of the pituitary effluent in horses is a useful method for investigating the release of pituitary hormones in loco (Irvine and Alexander 1987). Adrenocorticotropic hormone (ACTH) and arginine vasopression (AVP) concentrations in plasma collected from the intercavemous sinus, which receives all the pituitary outflow, were several times greater than those measured in peripheral plasma (Redekopp et at 1986). However, no studies evaluating the pituitary contribution to endogenous opioid secretion have been reported in the equine species. Cerebrospinal fluid (CSF) directly reflects CNS ...
Is the thoroughbred race-horse under chronic stress? Thoroughbred fillies were divided into three groups according to age: group 1, 7 fillies aged 1 to 2 years (G1) starting the training program; group 2, 9 fillies aged 2 to 3 years (G2) in a full training program; group 3, 8 older fillies 3 to 4 years of age (G3) training and racing. Blood samples were collected weekly from July to December. Cortisol was quantified using a solid phase DPC kit. The intra- and interassay coefficients of variation were 12.5% and 15.65% and sensitivity was 1.9 +/- 0.2 nmol/l. The semester average of cortisol levels varied between groups: G1 = 148.8 +/- 6.7, G2 = 12...
[Cortisol levels in blood and urine of trotting horses]. Statistical analysis of normally occurring cortisol levels in serum and urine of horses served to recommend thresholds for this corticosteroid in these body fluids, as application of exogenous cortisol as well as ACTH may elevate the cortisol concentrations above the proposed threshold. The present study contributes to the general issue of how to establish thresholds for trotting horses upon sportive examination. 100 randomly selected post competition serum and urine samples, respectively, were submitted to cortisol analysis by means of HPLC. Concentrations of the endogenous corticosteroid in ...
Stress response to chronic inflammation in the horse. Five clinically healthy Thoroughbred geldings were injected with Freund's adjuvant 3 times to induce a chronic inflammatory response. Blood was collected at various times before and after adjuvant administration. Clinical responses (rectal temperature and general demeanor) were also monitored. Adjuvant injection induced increases in rectal temperature and plasma fibrinogen concentration (maximum levels measured were mean +/- s.d. 39.7 +/- 0.5 degrees C and 8.2 +/- 0.3 g/l, respectively), indicative of an inflammatory response. A mild clinical depression was also observed in the horses for 24 h...
A case of a pony with Cushing’s disease. The pars intermedia of the pituitary gland, and plasma ACTH and cortisol levels in the pony, which was first diagnosed in Japan as indicating equine Cushing's disease, were examined by immunohistochemistry and radioimmunoassay, respectively. The pars intermedia was greatly enlarged and most of its cells were immunoreactive for antisera to both adenocorticotropic hormone (ACTH) and beta-endorphin (beta-End). The plasma ACTH level was elevated when clinical symptoms appeared. The present results reveal that equine Cushing's disease in this pony was induced by the hypersecretion of ACTH and beta-...
Results of a combined dexamethasone suppression/thyrotropin-releasing hormone stimulation test in healthy horses and horses suspected to have a pars intermedia pituitary adenoma. To evaluate results of a combined dexamethasone suppression/thyrotropin-releasing hormone (TRH) stimulation test in horses suspected clinically to have a pars intermedia pituitary adenoma (PIPA). Methods: Case-control study. Methods: 7 healthy adult horses and 5 horses suspected to have a PIPA. Methods: A baseline blood sample was collected, and dexamethasone (40 micrograms/kg [18 micrograms/lb] of body weight, IV) was administered; a second blood sample was collected 3 hours later, and TRH (1.1 mg, IV) was administered; serial blood samples were collected 15, 30, 45, 60, and 90 minutes and 21...
Validation of nonradioactive chemiluminescent immunoassay methods for the analysis of thyroxine and cortisol in blood samples obtained from dogs, cats, and horses. The performances of a radioimmunoassay method, a chemiluminescent immunoassay method, and a chemiluminescent-enzyme immunoassay method were evaluated for the analysis of cortisol and total thyroxine in blood samples obtained from dogs, cats, horses, and humans (reference samples). The analysis of cortisol in human and animal samples exhibited good precision, linearity, and recovery. The 3 methods gave comparable values for the ACTH-induced increase and the dexamethasone-induced decrease in cortisol concentrations in animal samples. The recoveries of total thyroxine from human samples, analyzed...
Endocrine changes in cerebrospinal fluid, pituitary effluent, and peripheral plasma of anesthetized ponies. To investigate the effects of inhalation and total IV anesthesia on pituitary-adrenal activity in ponies. Methods: 9 healthy ponies: 5 geldings and 4 mares. Methods: Catheters were placed in the cavernous sinus below the pituitary gland and in the subarachnoid space via the lumbosacral space. After 72 hours, administration of acepromazine was followed by induction of anesthesia with thiopentone and maintenance with halothane (halothane protocol), or for the IV protocol, anesthesia induction with detomidine and ketamine was followed by maintenance with IV infusion of a detomidine-ketamine-guaif...
Effect of insulin-induced hypoglycaemia on secretion patterns and rates of corticotrophin-releasing hormone, arginine vasopressin and adrenocorticotrophin in horses. To study the effect of hypoglycaemia on secretion rates of corticotrophin-releasing hormone (CRH), arginine vasopressin (AVP) and ACTH in a non-ruminant species, a non-surgical method was used to collect pituitary venous (PitVen) blood every 0.5 or 1 min from seven horses before and after insulin administration (0.4 U/kg i.v.). To assess the effect of PitVen cannulation on results, peripheral hormones were also measured before and after insulin in five horses without PitVen cannulae. Insulin administration lowered plasma glucose in all horses (P < 0.0001; paired t-test). Cortisol concentrat...
Cortisol concentrations in post competition horse urine: a French and British survey. The purpose of the present report was to estimate the population parameters of cortisol concentrations in urine, an endogenous hormone used as a 'doping' agent and for which an international threshold (1.0 micrograms/ml) has been proposed. Two data bases (French and UK) corresponding to 112 and 142 samples, respectively were considered. Urine was collected under specific post competition conditions. Cortisol concentrations were obtained by validated methods (HPLC for the French samples, and GC-MS for UK samples). No difference was observed between the 2 data sets and statistical analyses were ...