The pituitary gland in horses is a small, yet significant endocrine organ located at the base of the brain. It is responsible for producing and releasing hormones that regulate various physiological processes, including growth, metabolism, and reproduction. The gland is divided into two main parts: the anterior pituitary, which secretes hormones such as adrenocorticotropic hormone (ACTH) and growth hormone (GH), and the posterior pituitary, which releases hormones like vasopressin and oxytocin. Changes or dysfunctions in pituitary function can lead to conditions such as pituitary pars intermedia dysfunction (PPID), commonly known as equine Cushing's disease, which affects older horses. This page compiles peer-reviewed research studies and scholarly articles that explore the structure, function, and clinical implications of the pituitary gland in equine health.
Viviani P, Ragno VM, Parker S, Montgomery JB.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...
Teague P, Dark M, Verdugo D, Freeman D, McFarlane D.The equine pancreas remains understudied, particularly in the context of endocrine disease. This study aimed to characterize regional islet distribution and composition in the normal equine pancreas and investigate how hyperinsulinemia (HI) and pituitary pars intermedia dysfunction (PPID) influence pancreatic islet morphology and hormone expression. In the first experiment, pancreas samples from eight healthy horses were collected and analyzed across three anatomical locations: left lobe, body, and right lobe. The left lobe exhibited a greater relative islet area and perimeter compared to the ...
Stapley E, Gillespie-Harmon C, Waxman S, Farr A, Bertin FR.The frequency of comorbidities in horses with pituitary pars intermedia dysfunction (PPID) in first-opinion practice is unknown. It is hypothesized that horses with PPID would have more frequent medical events and be euthanized at a younger age. Unassigned: This was a case-control retrospective study. Medical records ranging from 1996 to 2024 including 132 horses diagnosed with PPID and 274 controls matched by age and breed were reviewed. Variables associated with PPID were evaluated with a Fisher exact or Mann-Whitney U test followed by conditional logistic regression. Results were reported a...
Page AE, McPeek JL, Carattini S, McGreevy E, Adam E.The goal of this project was to examine the metabolic effects of IA methylprednisolone acetate (MPA) following injection into multiple low-motion joints. Unassigned: Six 3-year-old geldings without pituitary pars intermedia dysfunction or insulin dysregulation were randomly injected with 20 mg of IA MPA/joint (80 mg total; bilateral distal hock joints) or an equal volume of saline. Serial blood samples were collected for resting ACTH, cortisol, insulin, and glucose, as well as insulin and glucose following repeated low-dose oral sugar tests. Treatments were crossed over after a 6-week washout,...
Fouché N, Howard J, Gerber V, Billmann P, Farinha do Sul M, Christen G, Bruckmaier R, Philipona C, Schmutz NB, Gross J.β-endorphin, a proopiomelanocortin (POMC)-derived peptide secreted by pars intermedia melanotropes, may play a significant but underexplored role in pituitary pars intermedia dysfunction (PPID) pathophysiology and diagnosis. This study aimed to (1) validate a commercially available human β-endorphin enzyme-linked immunosorbent assay (ELISA) kit for equine samples, and (2) compare β-endorphin concentrations between horses with PPID and healthy controls. Assay validation included the generation of standard curves using purified synthetic equine β-endorphin and human β-endorphin standards, w...
Parmantier S, Kyriazopoulou P, McClendon M, Adams A, Murphy BA.Fifty-two horses aged >15 years, diagnosed with pituitary pars intermedia dysfunction (PPID), and displaying hypertrichosis were recruited via an online survey of PPID horse owners. From mid-December, group T ( = 29) wore Equilume light masks extending photoperiod to 15 h daily, while group C1 ( = 23) remained under natural photoperiod. As 85% (44/52) of recruited study horses received pergolide medication, a second unmedicated PPID research herd (C2; = 17) was recruited and remained under natural photoperiod. Hair coat samples, shedding and body condition scores were collected monthly by own...
Massardi E, Gaudenzi G, Carra S, Oldani M, Rybinska I, Persani L, Vitale G.Cushing's disease (CD) is a rare neuroendocrine disorder caused by ACTH-secreting pituitary adenomas, presenting significant diagnostic and therapeutic challenges. Given the evolutionary conservation of the hypothalamic-pituitary-adrenal axis, this review explores the translational value of spontaneous CD forms in dogs, horses, cats, small mammals, and rats, as well as of experimental models in mice, rats, and zebrafish. Dogs are the most studied, showing strong molecular and clinical similarities with human CD, making them valuable for preclinical drug and diagnostic research. While equine an...
Menzies-Gow NJ.Pituitary pars intermedia dysfunction (PPID) is a common, slowly progressive, neurodegenerative disorder of the older horse. Oxidative damage to the hypothalamic periventricular neurons results in loss of dopaminergic inhibition of the pars intermedia region of the pituitary gland. Consequently, there is increased production of the pro-opiomelanocortin (POMC)-derived hormones normally produced by this region, as well as initial melanocyte hypertrophy and hyperplasia, followed by adenomatous change. Clinical signs that are highly suggestive of the disease are generalised and regional hypertrich...
Bailey VN, Gilbert BM, Vetter M, Oberhaus EL.The mechanism by which photoperiod influences the hypothalamic-pituitary-gonadal (HPG) axis and regulates seasonal reproduction in horses has yet to be fully elucidated. The hypophyseal pars tuberalis (PT) has been indicated as a critical site for the transduction of melatonin signals through melatonin-responsive, PT-specific cells that produce thyroid-stimulating hormone (TSH) in many mammalian species. However, this has yet to be investigated in horses. The objective of this study was to explore the interaction of melatonin and thyroid-stimulating hormone in the equine HPG axis. Pituitaries ...
Murase H, Wachi S, Matsuyama R, Makita K, Sato F.Pituitary pars intermedia dysfunction (PPID) is an age-related disease considered to have a negative impact on fertility. To understand the true impact of PPID on fertility, the influence of age must be considered. Objective: This study aimed to assess the impact of PPID on fertility while accounting for the effect of aging. Methods: A total of 332 Thoroughbred mares aged 10-20 years and managed across 137 private farms in Hidaka, Hokkaido, Japan were classified as PPID, equivocal, or non-PPID based on plasma adrenocorticotropic hormone concentration in 2019 and 2020. The prevalence of PPID an...
Osorio-Cardona JJ, Usuga-Moreno VM, Martínez-Aranzales JR.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...
Cravana C, Medica P, Fazio E, Satué K, Brancato G, La Fauci D, Bruschetta G.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...
Davis EL, Wood AD, Potier JFN.Prevalence of endocrine disease in sport horses has been sparsely reported. They often compete well into their teenage years; thus, diagnosis and control of endocrine disease could be important to maintain performance and optimise health and welfare. The aim was to compare the prevalence of pituitary pars intermedia dysfunction (PPID), insulin dysregulation (ID) and metabolic obesity between sport and non-sport type breeds and assess disease progression. Blood samples submitted for plasma adrenocorticotropic hormone (ACTH), serum insulin or adiponectin were included in this study. Horses were ...
Stapley ED, Bertin FR.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 dysfunction a...
Galinelli NC, Bamford NJ, Erdody ML, Mackenzie SA, Warnken T, Harris PA, Sillence MN, Bailey SR.Due to the high frequency of laminitis reported for both conditions, the relationship between pituitary pars intermedia dysfunction (PPID) and insulin dysregulation (ID), and the potential role of dopamine in modifying insulin secretion, requires further investigation. Objective: To evaluate the effect of pergolide mesylate on insulin sensitivity and postprandial insulin and glucose responses in horses and ponies with ID, both with or without concurrent PPID. Methods: Randomised crossover study. Methods: Sixteen horses and ponies, comprising eight matched pairs (PPID+ID or ID-only), were given...
Johnston TJ, Stewart AJ, Dryburgh EL, Bertin FR.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...
Cash CM, de Laat MA.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...
Galinelli NC, Bamford NJ, Erdody ML, Warnken T, de Laat MA, Sillence MN, Harris PA, Bailey SR.The role of dopamine in the regulation of insulin secretion in horses is poorly understood and requires further investigation. Pituitary pars intermedia dysfunction (PPID) is associated with decreased activity of dopaminergic neurons which normally suppress peptide hormone secretion from the pituitary pars intermedia. A high proportion of horses with PPID also have insulin dysregulation (ID), characterised by post-prandial hyperinsulinaemia and/or tissue insulin resistance, which are risk factors for the development of laminitis. The aim of this study was to investigate the effects of alpha-me...
Hallowell KL, Dembek K, Horne CR, Knych HK, Messenger KM, Schnabel LV.Steroid-associated laminitis remains a major concern with use of corticosteroids in horses. Individual case factors such as joint pathology, pre-existing endocrinopathies, or corticosteroid type, dose, and timing influencing steroid-induced laminitis risk have not been investigated. This study aimed to determine if systemic absorption of triamcinolone acetonide (TA) varies between intrasynovial (antebrachiocarpal) and extrasynovial (sacroiliac) injection sites, and to determine the effects of TA absorption on glucose, insulin, cortisol, and adrenocorticotropic hormone (ACTH). Twenty adult hors...
Melchert M, Aurich J, Ertl R, Reichart U, Walter I, Gautier C, Kaps M, Aurich C.Mares resume ovarian activity rapidly after foaling. Besides follicle-stimulating hormone (FSH) and luteinizing hormone (LH), the pituitary synthesizes prolactin and growth hormone which stimulate insulin-like growth factor (IGF) synthesis in the liver. We tested the hypothesis that follicular growth is initiated already antepartum, mares with early and delayed ovulation differ in IGF-1 release and that there is an additional IGF-1 synthesis in the placenta. Plasma concentrations of LH, FSH, IGF-1, IGF-2, activin and prolactin. IGF-1, IGF-2, prolactin and their receptors in placental tissues w...
Nielsen MK, Finnerty CA, Ripley NE, Page AE, McClendon ME, Adams AA.Anthelmintic performance against equine cyathostomins can be evaluated by two different non-terminal measures; the Fecal Egg Count Reduction Test (FECRT) and the Egg Reappearance Period (ERP). Most available FECRT and ERP data have been determined in populations of young horses, and very little information is available from mature and senior horses. Furthermore, it is unknown how commonly occurring equine endocrine disorders such as Insulin dysregulation (ID) and Pituitary pars intermedia dysfunction (PPID) may interfere with these measurements, but it has been suggested that horses with these...
Horner A, Bamford NJ, Stear MJ, Piedrafita D, Jabbar A, Hughes KJ, El-Hage CM, Preston S.Pituitary pars intermedia dysfunction (PPID) is the most common endocrine disorder of older horses. Immune dysfunction in horses with PPID could increase susceptibility to infectious diseases, including strongyle infections; however, few data are available. The aim of this study was to determine if horses with PPID had increased strongyle faecal egg counts (FEC) compared with control horses, over a fourteen-week period in Victoria, Australia. Clinical signs and plasma adrenocorticotropic hormone (ACTH) concentrations were used to categorise horses into PPID (n=14) or control (n=31) groups. Fae...
Giers J, Bartel A, Kirsch K, Müller SF, Horstmann S, Gehlen H.After submaximal exercise, blood values of eventing horses show physiological reactions. This prospective longitudinal study investigated blood parameters in 20 elite eventing horses before and after two-four-star cross-country rides. Using a mixed model adjusting for plasma volume shift, we assessed exercise-dependent parameters and compared blood values with reference ranges for healthy horses at rest. Following exercise, cortisol, triiodothyronine (T3) and thyroxine (T4) showed short-term increases, and superoxide-dismutase showed a small short-term increase. Hepatic values showed short-ter...
Waitt Wolker LH, Black A, Lee JK.Clinical and histologic examination of a 12-y-old client-owned Quarter Horse gelding with pituitary pars intermedia dysfunction revealed dermatitis, cellulitis, and osteomyelitis caused by , confirmed by a PCR assay. This novel presentation of a fungal disease in a horse was characterized by aggressive local invasion and failure to respond to all medical therapy attempted over a 1-y period. Treatments included systemic and topical antifungals, anti-inflammatories, and use of cellular matrices. Surgical excision was not attempted but should be strongly considered early in the disease process in...
Sundra T, Kelty E, Rossi G, Rendle D.Dopaminergic agonists are accepted as the most effective treatment for pituitary pars intermedia dysfunction. However, some horses are refractory to daily oral pergolide, the recommended registered treatment. Extended-release cabergoline (ERC) injection may offer an alternative. The objective of this retrospective case series was to describe clinical and endocrinological responses to ERC. Unassigned: Medical records of horses treated with weekly intramuscular injections of ERC (5 mg/mL, BOVA Aus) at either 0.01 mg/kg (high dose, HD) ( = 10) or 0.005 mg/kg (low dose, LD) ( = 30) w...
de Preux M, Precht C, Guevar J, Graubner C, Thenhaus-Schnabel S, Buser L, Lukes A, Koch C.A 16-year-old warmblood mare was referred with a progressive history of behavioral changes and left-sided blindness. Following neuroanatomical localization to the forebrain, magnetic resonance imaging of the head revealed a well-delineated, 4.5 cm in diameter, round pituitary mass causing marked compression of the midbrain and optic chiasm. Euthanasia was recommended but declined by the owners. Veterinary specialists and a human neurosurgeon collaboratively prepared for surgical case management. A novel navigated transmandibular lateral transsphenoidal approach was developed to access the re...
Ireland JL, Lester A, Banse HE.Measurement of basal adrenocorticotropic hormone (ACTH) concentration is the most commonly used diagnostic test for pituitary pars intermedia dysfunction (PPID). Although several pre-analytical and analytical factors have been reported to affect basal ACTH concentrations in equids, the extent to which these have been evaluated in the context of PPID diagnosis is unclear. The objectives of this scoping review were to identify and systematically chart current evidence about pre-analytical and analytical factors affecting basal ACTH concentrations in adult domestic equids. Systematic searches of ...
Clark BL, Norton EM, Bamford NJ, Randhawa IAS, Kemp KL, McCue ME, Bertin FR, Stewart AJ.Insulin dysregulation (ID) is central to equine metabolic syndrome. There are limited epidemiological studies investigating dynamic testing of ID in ponies. Objective: To evaluate prevalence and risk factors for ID through dynamic testing of hyperinsulinaemia (DHI) and insulin resistance (IR). Methods: Cross-sectional. Methods: Sex, age, breed, height, cresty neck score (CNS), body condition score (BCS), laminitis, HMGA2:c.83G>A genotype and pituitary pars intermedia dysfunction (PPID) status were documented. Dynamic hyperinsulinaemia was diagnosed with an oral sugar test (OST) and IR with an ...
Colbath AC, Fortin JS, Burglass CM, Panek C, Vergara-Hernandez FB, Johnson TN, Robison CA, Logan AA, Nelson NA, Nielsen BD, Schott HC.Pathological fractures have been reported in equids with pituitary pars intermedia dysfunction (PPID) but their prevalence and pathogenesis is unknown. Objective: To compare: (1) bone mineral density (BMD) in weight bearing and nonweight bearing bones in PPID+ equids and aged and young PPID- controls; and (2) biomechanical properties of the fourth lumbar vertebral body in PPID+ equids and aged PPID- equids. Methods: Case-control study: five PPID+ equids and six aged and four young PPID- control horses. Methods: PPID status was based on clinical signs and necropsy examination of the pituitary g...
Ayala I, Martos NF, Silvan G, Gutierrez-Panizo C, Clavel JG, Illera JC.No detailed comparative data are available on the hormonal parameters of horses suffering from a number of diseases. The aim of our study was to measure concentrations of cortisol, adrenocorticotropic hormone (ACTH), serotonin, adrenaline and noradrenaline in horses with various diseases and following surgery, to assess the response of the HPA axis and adrenal medulla. Blood samples were obtained from six groups of horses comprising a total of 119 animals as follows: laminitis, acute abdominal syndrome (AAS), castration surgery, acute diseases, chronic diseases and healthy controls. Serum horm...
Porter JK, Thompson FN.Fescue toxicosis in livestock is due to ingestion of endophyte (Acremonium coenophialum) -infected tall fescue. Understanding mechanisms responsible for decreased calving and growth rates, delayed onset of puberty, and impaired function of corpora lutea in heifers at puberty consuming endophyte-infected fescue is an emerging field in reproductive toxicology. The condition decreases overall productivity through a reduction in reproductive efficiency, reduced weight gains, and lowered milk production. Reproduction in cattle may be further compromised by winter coat retention, increased susceptib...
Aurich C.Horses are long-day breeders. During the breeding season, cycle length is about 22 days with 5-7 days of oestrus. Gonadotroph cells are localized in the pars distalis as well the pars tuberalis of the pituitary and heterogeneity in the pattern of LH and FSH storage within the gonadotroph population is considered the basis for the differential regulation of gonadotrophin secretion throughout the reproductive cycle. No short and distinct periovulatory LH peak exists in the mare. The equine ovary has an extreme large size and weight. One to two major follicular waves develop per cycle. The preovu...
Donaldson MT, McDonnell SM, Schanbacher BJ, Lamb SV, McFarlane D, Beech J.The purpose of this study was to evaluate the variation in plasma adrenocorticotropic hormone (ACTH) concentration and dexamethasone suppression test (DST) results with season, age, and sex in healthy, pony mares (n=15) and pony stallions (n=14) living under semiferal conditions and horse mares (n=10) living at pasture. Plasma ACTH concentrations were measured in September 2002, and in January, May, and September 2003. DSTs were performed in January and September 2003. Plasma ACTH concentrations in September 2002 and September 2003 were similar and were significantly greater than in January an...
Eiler H, Frank N, Andrews FM, Oliver JW, Fecteau KA.To characterize the physiologic response to i.v. bolus injection of glucose and insulin for development of a combined glucose-insulin test (CGIT) in horses. Methods: 6 healthy mares and 1 mare each with pituitary adenoma and urolithiasis. Methods: Horses were given a CGIT (glucose, 150 mg/kg; insulin, 0.1 U/kg); results were compared with a singular i.v. glucose tolerance test (GTT; 150 mg/kg) and a singular i.v. insulin sensitivity test (IST; 0.1 U/kg). Healthy horses were also given a CGIT after receiving xylazine and undergoing stress. Results: Physiologically, the CGIT resulted in a 2-phas...
Bousfield GR, Butnev VY, Gotschall RR, Baker VL, Moore WT.There are two species for which both pituitary and placental gonadotropins are readily available, humans and horses. The human gonadotropins are better characterized than equine gonadotropins. Nevertheless, the latter are very interesting because they provide exceptions to some of the general structure-function principles derived from studies on human and other mammalian gonadotropins. For example, separate genes encode the hLH beta and hCG beta subunits while a single gene encodes eLH beta and eCG beta. Thus, eCG and eLH differ only in their oligosaccharide moieties and eLH is the only LH tha...
Comin A, Veronesi MC, Montillo M, Faustini M, Valentini S, Cairoli F, Prandi A.Stimulation of the hypothalamic-pituitary-adrenal (HPA) axis and elevated cortisol concentrations in fetal plasma are associated with foal maturity, viability and adaptation to independent life. However, non-invasive measurement of cortisol in hair samples has not yet been validated in horses. The current study developed a radioimmunoassay to analyse cortisol in horse hair and was used to measure cortisol hair concentration at birth and at 30 and 60 days of age as a retrospective study of HPA axis activity. Cortisol was detectable in the hair of foals from birth until 2 months, but decreased w...
Sherman GB, Wolfe MW, Farmerie TA, Clay CM, Threadgill DS, Sharp DC, Nilson JH.Equine (e) CG and LH beta-subunits have identical amino acid sequences, including an extended carboxyl-terminal peptide (CTP). This suggests that unlike the corresponding human genes, the beta-subunits of eCG and eLH may be encoded by a single gene and share a common proximal promotor region. To explore this, we isolated and characterized the eLH/CG beta gene(s). Data from Southern analyses suggest that the eCG beta and eLH beta subunits are products of the same single copy gene (eLH/CG beta). Overlapping fragments of the eLH/CG beta gene and cDNA were amplified from equine genomic DNA and pit...
Hurcombe SD, Toribio RE, Slovis N, Kohn CW, Refsal K, Saville W, Mudge MC.Sepsis is an important cause for neonatal foal mortality. The hypothalamic-pituitary-adrenal axis (HPAA) responses to sepsis are well documented in critically ill humans, but limited data exist in foals. The purpose of this study was to evaluate the HPAA response to sepsis in foals, and to associate these endocrine changes with survival. Objective: Blood concentrations of arginine vasopressin (AVP), adrenocorticotropin hormone (ACTH), and cortisol will be higher in septic foals as compared with sick nonseptic and healthy foals. The magnitude of increase in hormone concentration will be negativ...
Alexander SL, Irvine CH, Ellis MJ, Donald RA.We have used the technique which we have developed for collecting pituitary venous blood from conscious, undisturbed horses to study the effect of acute vigorous exercise on the secretion of CRF, arginine vasopressin (AVP) and ACTH. Pituitary venous (pit) blood was collected every 1-5 min from nine trained racehorses at rest in the stable. The horses then trotted quietly for 10 min, after which they galloped as fast as possible for 4-6 min, before returning to the stable where sampling continued. In Exp 1 (n = 5) no blood samples were taken during exercise, whereas in Exp 2 (n = 4), pit blood ...
Heinrichs M, Baumgärtner W, Capen CC.Adenomas of the pars intermedia from 19 horses and normal pituitary glands from seven horses were evaluated histologically and immunocytochemically for adrenocorticotropic hormone (ACTH), alpha-melanocyte-stimulating hormone (alpha-MSH), beta-endorphin (beta-END), proopiomelanocortin (POMC), prolactin, neuron specific enolase, and glial fibrillary acidic protein (GFAP). The 26 horses ranged in age from 7 to 31 years. Histologically, all adenomas had a uniform pattern characterized by cords of large columnar cells forming palisades and pseudoacini separated by a delicate fibrovascular stroma. I...
Gold JR, Divers TJ, Barton MH, Lamb SV, Place NJ, Mohammed HO, Bain FT.Little information exists on the hypothalamic-pituitary-adrenal axis in septic foals. Objective: The plasma concentrations of adrenocorticotropin (ACTH) and cortisol are expected to be higher in septic foals as compared to normal foals. The concentrations of hormones in septic foals also are expected to differ further depending upon survival. Methods: Twenty-eight control foals and 46 septic foals 11 or a positive blood culture. The control foals were age matched to the septic foals in the study. ACTH and cortisol concentrations were measured by a chemiluminescent immunoassay system. Results: ...
Allen WR.Four separate components combine to produce the progesterone and biologically active 5 alpha-reduced pregnanes needed to maintain pregnancy in the mare. The primary corpus luteum (CL) is prolonged beyond its cyclical lifespan by the down-regulation of endometrial oxytocin receptors to prevent activation of the luteolytic pathway and its waning progesterone production is supplemented from day 40 of gestation by the formation of a series of accessory CL which develop in the maternal ovaries as a result of the gonadotrophic actions of pituitary FSH and the equine chorionic gonadotrophin (eCG). Fr...
Hart KA, Slovis NM, Barton MH.Transient hypothalamic-pituitary-adrenal (HPA) axis dysfunction occurs frequently in critically ill humans and impacts survival. The prevalence and impact of HPA axis dysfunction in critically ill neonatal foals are not well characterized. Objective: (1) HPA axis dysfunction occurs in hospitalized neonatal foals, and is characterized by inappropriately low basal serum cortisol concentration or inadequate cortisol response to exogenous adrenocorticotropic hormone (ACTH); (2) hospitalized foals with HPA axis dysfunction have more severe disease and are less likely to survive than hospitalized fo...
Ferlazzo A, Cravana C, Fazio E, Medica P.The review discusses the hormonal changes during exercise stress. The exercise generally produces a rise of adrenaline (A), noradrenaline (NA), adrenocorticotropic hormone (ACTH), cortisol, glucagon, growth hormone, arginine vasopressine, etc., and a drop of insulin. The hormonal events during reestablishment of homeostasis due to exercise stress can be divided into a catabolic phase, with decreased tolerance of effort, and reversible biochemical, hormonal and immunological changes, and an anabolic phase, with a higher adaptive capacity, and enhanced performance. The two main hormonal axes act...
de Graaf-Roelfsema E, Keizer HA, van Breda E, Wijnberg ID, van der Kolk JH.Overtraining is an imbalance between training and recovery leading to symptoms associated with a neuroendocrine dysbalance called the overtraining syndrome, a disease characterized by behavioral, emotional and physical symptoms similar with depression. Although the prevalence of overtraining is high in human and equine athletes, at present no sensitive and specific test is available to prevent or diagnose overtraining. Nowadays, it is believed that combination of different (hormonal) parameters appear to be the best indicators of overtraining. Therefore, this review provides a summary of previ...
Stewart AJ, Hackett E, Bertin FR, Towns TJ.Plasma adrenocorticotropic hormone (ACTH) and serum cortisol concentrations increase with illness-associated stress. Dynamics of plasma ACTH and serum cortisol concentrations in adult horses with systemic illness are undocumented. Objective: To determine whether ACTH and cortisol concentrations and the ACTH/cortisol ratio vary with survival, the presence of systemic inflammatory response syndrome (SIRS), or ischemic gastrointestinal lesions at admission, or throughout hospitalization. Methods: One hundred fifty-one adult horses. Methods: Prospective study measuring serum cortisol and plasma AC...
Beech J, Boston R, Lindborg S, Russell GE.To compare the effect of thyrotropin-releasing hormone (TRH) administration on endogenous ACTH concentrations in healthy horses and those with pituitary pars inter-media hyperplasia and compare the test with the dexamethasone suppression test (DST). Methods: Prospective case series. Methods: 15 horses with clinical signs of pituitary pars intermedia dysfunction (PPID), 4 horses with equivocal signs of PPID, and 29 horses without signs of PPID. Methods: ACTH concentrations prior to and after administration of TRH were measured 61 times in 48 horses. Results of the DST (cortisol response) were c...
Bousfield GR, Sugino H, Ward DN.The beta subunits of equine lutropin and equine chorionic gonadotropin were incubated in 0.013 N HCl for 30 min at 110 degrees C and separated into two fragments by reverse-phase high performance liquid chromatography. The amino acid and carbohydrate compositions of both fragments from each subunit were analyzed. The results demonstrated that equine lutropin-beta has a glycosylated COOH-terminal extension that differs only in carbohydrate composition from the COOH-terminal portion of equine chorionic gonadotropin-beta. This is the first demonstration of a glycosylated COOH-terminal extension i...
Fitzgerald BP, McManus CJ.The objectives of this study were to compare the timing and mechanisms controlling the onset of anestrus in young and mature mares treated either continuously with melatonin and in those that remained untreated. Changes in body weight, subcutaneous body fat measured to provide an estimate of total body fat, and circulating concentrations of leptin were compared throughout the 1-yr experimental period. The results demonstrate that in young mares the timing of anestrus occurs significantly earlier in the year than in mature mares and that mature mares are more likely to exhibit continuous reprod...
Smith PL, Bousfield GR, Kumar S, Fiete D, Baenziger JU.Equine chorionic gonadotropin (eCG) and lutropin (eLH) are heterodimeric glycoprotein hormones which are synthesized in the placenta and pituitary, respectively. The beta subunits of eCG and eLH, like their alpha subunits, arise from a single gene and have identical amino acid sequences. In contrast, the beta subunits of CG and LH in primates arise from different genes and differ in sequence. We have examined the structures of the Asn-linked oligosaccharides on eCG and eLH. eCG bears di- and tri-branched Asn-linked oligosaccharides terminating with Sia alpha 2,3 or 6Gal beta 1,4GlcNAc. In cont...
Horn F, Windle JJ, Barnhart KM, Mellon PL.The molecular mechanisms for the development of multiple distinct endocrine cell types in the anterior pituitary have been an area of intensive investigation. Though the homeodomain protein Pit-1/GHF-1 is known to be involved in differentiation of the somatotrope and lactotrope lineages, which produce growth hormone and prolactin, respectively, little is known of the transcriptional regulators important for the gonadotrope cell lineage, which produces the glycoprotein hormones luteinizing hormone and follicle-stimulating hormone. Using transgenic mice and transfection into a novel gonadotrope ...
Miller MA, Pardo ID, Jackson LP, Moore GE, Sojka JE.Functional evaluation of the pars intermedia (PI) is required for the early diagnosis of equine pituitary PI dysfunction (PPID), yet most assays target the hypothalamic-pituitary-adrenal axis, which regulates the pars anterior. In contrast, the PI is regulated by dopaminergic tone from hypothalamic neurons. Loss of dopaminergic inhibition is hypothesized to cause the PI hypertrophy and hyperplasia that result in the clinical manifestations of PPID. Domperidone, a dopamine receptor antagonist, should exacerbate the loss of dopaminergic inhibition in horses with PPID and increase the release of ...
Sugino H, Bousfield GR, Moore WT, Ward DN.The complete amino acid sequence of the beta-subunit of equine chorionic gonadotropin (eCG beta) has been established by both automated Edman and manual 5-dimethylaminonaphthalene-1-sulfonyl-Edman degradations. Specific fragments were produced by cleavage with Staphylococcus aureus V8 protease, trypsin, or dilute HCl. For the sequence analyses of the heavily glycosylated COOH-terminal portion, a chemical deglycosylation procedure with trifluoromethanesulfonic acid was employed. The peptide chain of eCG beta consists of 149 amino acid residues. Five or more oligosaccharide chains are attached t...
Abbara A, Ratnasabapathy R, Jayasena CN, Dhillo WS.The Kiss1 gene encodes a 145-amino acid pre-peptide, kisspeptin, which is cleaved into smaller peptides of 54, 14, 13, and 10 amino acids. This chapter reviews in detail the effects of kisspeptin on gonadotropin secretion in non-human mammals. Studies of kisspeptin's effects have included both acute and chronic administration regimens via a number of administration routes. Acute kisspeptin stimulates gonadotropin secretion in a wide range of species of non-human mammals, including rats, mice, hamsters, sheep, pigs, goats, cows, horses, and monkeys. In general, the stimulatory effect of kisspep...
Sarkar DK, Smith GC, Fink G.We have investigated the effect of manipulating central catecholamines on the timing of puberty (as assessed by vaginal opening) in female rats and the surge of luteinizing hormone (LH) and gonadotropin releasing hormone (GnRH) induced by pregnant mare serum gonadotropin (PMSG) in immature female rats. Manipulation of the catecholamines was carried out with either 6-hydroxydopamine (6-OHDA) administered with or without either desipramine (DMI) or pargyline, or alpha-methyl-p-tyrosine (alpha-MPT). The neonatal administration of 6-OHDA delayed puberty, an effect which was potentiated by pretreat...
Dhakal P, Hirama A, Nambo Y, Harada T, Sato F, Nagaoka K, Watanabe G, Taya K.The present study was conducted to elucidate the profile of circulating gonadotropins and gonadal hormones from birth to puberty and relationship between gonadal seasonality and hormonal secretion in both sexes of Thoroughbred horses. Spring-born colts (n=6) and fillies (n=9) were blood sampled weekly from jugular vein from birth to 60 weeks of age. Circulating FSH, LH, prolactin, testosterone, progesterone, estradiol-17β, and immunoreactive (ir)-inhibin were measured by radioimmunoassay. In both sexes, the steroid hormones levels were remarkably high at birth, rapidly dropped within a week a...
Stogdale L.The nomenclature of human diabetes mellitus (DM) has been revised, and this classification has been accepted throughout the medical world and literature. The major categories of diabetes are: insulin-dependent DM, type I or IDDM; noninsulin-dependent DM, type II or NIDDM; secondary DM or type S; impaired glucose tolerance, IGT; gestational diabetes; and previous abnormality of glucose tolerance, PrevAGT. A review of the literature has shown that over half of the documented diabetic dogs, with a single medical diagnosis, appear to be type I, IDDM, with a substantial proportion being type S, and...
Keenan DM, Alexander S, Irvine C, Veldhuis JD.Cortisol is an important mediator of physiological stress responses. Hypothalamic CRH and arginine vasopressin (AVP) and pituitary ACTH, in addition to hypothalamic and pituitary cortisol feedback, regulate cortisol secretion. Importantly, joint interactions among the four, rather than the signal of any one hormone, govern this life-preserving axis. Quantifying in vivo strength of such joint interactions has been difficult, especially without direct injection of cortisol, CRH, AVP, or ACTH. The goal of the present research was to estimate these joint feedback and feedforward interactions in vi...
Dhakal P, Tsunoda N, Nakai R, Kitaura T, Harada T, Ito M, Nagaoka K, Toishi Y, Taniyama H, Gen W, Taya K.Changes in follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin, immunoreactive(ir)-inhibin, testosterone, estradiol-17β, and insulin-like growth factor (IGF)-I in Thoroughbred stallions along with changes in prolactin secretion in geldings were studied. The correlations of day-length with changes in the concentrations of these hormones were also studied. Five stallions and thirteen geldings were employed to draw blood samples in monthly basis and radioimmunoassay was performed to measure these hormones. All hormones showed a seasonal pattern, the levels being highest durin...
