{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,18]],"date-time":"2026-09-18T08:57:58Z","timestamp":1789721878220,"version":"4.0.1"},"reference-count":36,"publisher":"American Veterinary Medical Association (AVMA)","issue":"2","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["javma"],"published-print":{"date-parts":[[2012,7,15]]},"abstract":"<jats:title>Abstract<\/jats:title>\n<jats:p><jats:bold>Objective<\/jats:bold>\u2014To determine whether seasonal variations exist in endogenous plasma ACTH, plasma \u03b1-melanocyte\u2014stimulating hormone (\u03b1-MSH), serum cortisol, and serum insulin concentrations and in the results of a dexamethasone suppression test for older, clinically normal geldings in Alabama.<\/jats:p>\n<jats:p><jats:bold>Design<\/jats:bold>\u2014Cohort study.<\/jats:p>\n<jats:p><jats:bold>Animals<\/jats:bold>\u201415 healthy mixed-breed geldings (median age, 14 years).<\/jats:p>\n<jats:p><jats:bold>Procedures<\/jats:bold>\u2014Sample collection was repeated monthly for 12 months. Dexamethasone (0.04 mg\/kg [0.02 mg\/lb], IM) was administered and cortisol concentrations were determined at 15 and 19 hours. Radioimmunoassays were used to measure ACTH, \u03b1-MSH, cortisol, and insulin concentrations at each testing time. Hormone concentrations were compared between months via repeated-measures ANOVA and correlated with age within each month.<\/jats:p>\n<jats:p><jats:bold>Results<\/jats:bold>\u2014A significant time effect was found between months for \u03b1-MSH and insulin concentrations. Endogenous cortisol and ACTH concentrations remained within existing reference ranges. Significant correlations were detected between age and ACTH concentration for several fall and winter months and between age and insulin concentration for September.<\/jats:p>\n<jats:p><jats:bold>Conclusions and Clinical Relevance<\/jats:bold>\u2014Older horses have higher ACTH concentrations in several fall and winter months and higher insulin concentrations in September than do younger horses. Seasonally specific reference ranges are required for \u03b1-MSH and insulin concentrations, with significantly higher concentrations detected in the fall. Practitioners should be advised to submit samples only to local laboratories that can provide such reference ranges for their local geographic region.<\/jats:p>","DOI":"10.2460\/javma.241.2.241","type":"journal-article","created":{"date-parts":[[2012,7,5]],"date-time":"2012-07-05T17:31:43Z","timestamp":1341509503000},"page":"241-248","source":"Crossref","is-referenced-by-count":40,"title":["Seasonal variation in results of diagnostic tests for pituitary pars intermedia dysfunction in older, clinically normal geldings"],"prefix":"10.2460","volume":"241","author":[{"given":"Christopher M.","family":"Schreiber","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Allison J.","family":"Stewart","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Eddy","family":"Kwessi","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ellen N.","family":"Behrend","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"James C.","family":"Wright","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Robert J.","family":"Kemppainen","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Katherine A.","family":"Busch","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1272","reference":[{"key":"ref1","series-title":"Vet Clin North Am Equine Pract","first-page":"237","article-title":"Pituitary pars intermedia dysfunction: equine Cushing's disease","volume":"18","author":"Schott","year":"2002"},{"key":"ref2","series-title":"Vet Clin North Am Equine Pract","first-page":"533","article-title":"Equine Cushing's disease","volume":"18","author":"McCue","year":"2002"},{"key":"ref3","series-title":"Vet Rec","first-page":"594","article-title":"Equine pituitary neoplasia\u2014a clinical report of 21 cases (1990\u20131992)","volume":"133","author":"van der Kolk","year":"1993"},{"key":"ref4","series-title":"J Am Vet Med Assoc","first-page":"1123","article-title":"Evaluation of suspected pituitary pars intermedia dysfunction in horses with laminitis","volume":"224","author":"Donaldson","year":"2004"},{"key":"ref5","series-title":"J Am Vet Med Assoc","first-page":"627","article-title":"Diagnostic testing for pituitary pars intermedia dysfunction in horses","volume":"204","author":"Dybdal","year":"1994"},{"key":"ref6","series-title":"J Vet Intern Med","first-page":"1","article-title":"Plasma adrenocorticotropin concentration in healthy horses and in horses with clinical signs of hyperadrenocorticism","volume":"10","author":"Cou\u00ebtil","year":"1996"},{"key":"ref7","series-title":"Domest Anim Endocrinol","first-page":"276","article-title":"Alpha-melanocyte stimulating hormone release in response to thyrotropin releasing hormone in healthy horses, horses with pituitary pars intermedia dysfunction and equine pars intermedia explants","volume":"30","author":"McFarlane","year":"2006"},{"key":"ref8","series-title":"J Am Vet Med Assoc","first-page":"417","article-title":"Adrenocorticotropin concentration following administration of thyrotropin-releasing hormone in healthy horses and those with pituitary pars intermedia dysfunction and pituitary gland hyperplasia","volume":"231","author":"Beech","year":"2007"},{"key":"ref9","series-title":"J Vet Intern Med","first-page":"217","article-title":"Variation in plasma adrenocorticotropic hormone concentration and dexamethasone suppression test results with season, age, and sex in healthy ponies and horses","volume":"19","author":"Donaldson","year":"2005"},{"key":"ref10","series-title":"Am J Vet Res","first-page":"1463","article-title":"Effects of season and sample handling on measurement of plasma \u03b1-melanocyte-stimulating hormone concentrations in horses and ponies","volume":"65","author":"McFarlane","year":"2004"},{"key":"ref11","series-title":"J Am Vet Med Assoc","first-page":"715","article-title":"Evaluation of plasma ACTH, \u03b1-melanocyte\u2013stimulating hormone, and insulin concentrations during various photoperiods in clinically normal horses and ponies and those with pituitary pars intermedia dysfunction","volume":"235","author":"Beech","year":"2009"},{"key":"ref12","series-title":"J Vet Intern Med","first-page":"650","article-title":"Seasonal variations in serum concentrations of selected metabolic hormones in horses","volume":"24","author":"Place","year":"2010"},{"key":"ref13","series-title":"Am J Vet Res","first-page":"122","article-title":"Hypertension and insulin resistance in a mixed-breed population of ponies predisposed to laminitis","volume":"69","author":"Bailey","year":"2008"},{"key":"ref14","series-title":"Vet J","first-page":"58","article-title":"The use of adrenocorticotrophic hormone as a potential biomarker of pituitary pars intermedia dysfunction in horses","volume":"185","author":"Lee","year":"2010"},{"key":"ref15","series-title":"J Vet Intern Med","first-page":"467","article-title":"Equine metabolic syndrome","volume":"24","author":"Frank","year":"2010"},{"key":"ref16","series-title":"Domest Anim Endocrinol","first-page":"355","article-title":"Preservative effect of aprotinin on canine plasma immunoreactive adrenocorticotropin concentrations","volume":"11","author":"Kemppainen","year":"1994"},{"key":"ref17","series-title":"Pflugers Arch","first-page":"11","article-title":"Plasma cortisol and beta-endorphin concentrations in trained and over-trained Standardbred racehorses","volume":"439","author":"Golland","year":"1999"},{"key":"ref18","series-title":"Equine Vet J","first-page":"219","article-title":"Exercise induced hormonal and metabolic changes in Thoroughbred horses: effects of conditioning and acepromazine","volume":"23","author":"Freestone","year":"1991"},{"key":"ref19","series-title":"J Anim Sci","first-page":"1936","article-title":"Plasma cortisol and ACTH concentrations in the warmblood horse in response to a standardized treadmill exercise test as physiological markers for evaluation of training status","volume":"78","author":"Marc","year":"2000"},{"key":"ref20","series-title":"Acta Endocrinol (Copenh)","first-page":"471","article-title":"In vivo evidence for dopaminergic regulation of the canine pituitary intermediate lobe","volume":"113","author":"Kemppainen","year":"1986"},{"key":"ref21","series-title":"Peptides","first-page":"1061","article-title":"Molecular forms of alpha-melanocyte-stimulating hormone in the canine pituitary anterior and intermediate lobe","volume":"13","author":"Young","year":"1992"},{"key":"ref22","series-title":"Am J Vet Res","first-page":"295","article-title":"Plasma concentrations of immunoreactive proopiomelanocortin peptides and cortisol in clinically normal cats","volume":"55","author":"Peterson","year":"1994"},{"key":"ref23","series-title":"Psychol Bull","first-page":"302","article-title":"Multivariate analysis of variance versus multiple univariate analysis","volume":"105","author":"Huberty","year":"1989"},{"key":"ref24","series-title":"J Endocrinol","first-page":"471","article-title":"Seasonal and photoperiod-induced changes in the secretion of alpha-melanocyte-stimulating hormone in Soay sheep: temporal relationships with changes in beta-endorphin, prolactin, follicle-stimulating hormone, activity of the gonads and growth of wool and horns","volume":"144","author":"Lincoln","year":"1995"},{"key":"ref25","series-title":"Neuroendocrinology","first-page":"309","article-title":"Photoperiod dependence of seasonal changes in pituitary content of melanocyte stimulating-hormone","volume":"30","author":"Logan","year":"1980"},{"key":"ref26","series-title":"J Anim Sci","first-page":"1594","article-title":"Effects of fescue toxicosis on reproduction in livestock","volume":"70","author":"Porter","year":"1992"},{"key":"ref27","series-title":"Equine Vet J","first-page":"295","article-title":"Serum insulin concentrations in horses, with equine Cushing's syndrome: response to a cortisol inhibitor and prognostic value","volume":"36","author":"McGowan","year":"2004"},{"key":"ref28","series-title":"J Am Vet Med Assoc","first-page":"1383","article-title":"Physical characteristics, blood hormone concentrations, and plasma lipid concentrations in obese horses with insulin resistance","volume":"228","author":"Frank","year":"2006"},{"key":"ref29","series-title":"J Am Vet Med Assoc","first-page":"1365","article-title":"Effect of dietary fructans and dexamethasone administration on the insulin response of ponies predisposed to laminitis","volume":"231","author":"Bailey","year":"2007"},{"key":"ref30","series-title":"J Vet Intern Med","first-page":"1167","article-title":"Association of season and pasture grazing with blood hormone and metabolite concentrations in horses with presumed pituitary pars intermedia dysfunction","volume":"24","author":"Frank","year":"2010"},{"key":"ref31","series-title":"Proceedings","article-title":"Obesity and insulin resistance","author":"Frank"},{"key":"ref32","series-title":"Am J Vet Res","first-page":"1247","article-title":"Hematologic and serum biochemical variables and plasma corticotropin concentration in healthy aged horses","volume":"59","author":"McFarlane","year":"1998"},{"key":"ref33","series-title":"J Vet Intern Med","first-page":"436","article-title":"Cytokine dysregulation in aged horses and horses with pituitary pars intermedia dysfunction","volume":"22","author":"McFarlane","year":"2008"},{"key":"ref34","series-title":"Neuroendocrinology","first-page":"349","article-title":"Combined dexamethasone\/CRH test in rats: hypothalamo-pituitary-adrenocortical system alterations in aging","volume":"64","author":"Hatzinger","year":"1996"},{"key":"ref35","series-title":"J Clin Endocrinol Metab","first-page":"2556","article-title":"Activity of the hypothalamic-pituitary-adrenal axis is altered by aging and exposure to social stress in female rhesus monkeys","volume":"85","author":"Gust","year":"2000"},{"key":"ref36","series-title":"Psychoneuroendocrinology","first-page":"392","article-title":"The HPA axis response to stress in women: effects of aging and fitness","volume":"30","author":"Traustad\u00f3ttir","year":"2005"}],"container-title":["Journal of the American Veterinary Medical 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