{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,16]],"date-time":"2026-07-16T19:12:02Z","timestamp":1784229122502,"version":"3.55.0"},"reference-count":31,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2026,4,7]],"date-time":"2026-04-07T00:00:00Z","timestamp":1775520000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Animals"],"abstract":"<jats:p>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 T4 was significantly higher in autumn than in spring in all the animals (p = 0.049) and significantly higher in donkeys than in horses (p = 0.0046). The concentration of ACTH was significantly higher in autumn than in spring in all animals (p = 0.00015) and significantly higher in donkeys than in horses and ponies (p = 0.001). The study results underscore the importance of utilizing seasonal hormone reference ranges specifically adapted for ponies and donkeys to accurately assess hormone secretion patterns in young animals. Reliance on reference values established for horses may lead to overinterpretation of hormone concentrations and misdiagnosis of endocrine disease in healthy donkeys or ponies.<\/jats:p>","DOI":"10.3390\/ani16071124","type":"journal-article","created":{"date-parts":[[2026,4,7]],"date-time":"2026-04-07T12:03:47Z","timestamp":1775563427000},"page":"1124","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Adrenocorticotropic Hormone and Thyroxine Concentrations in Young Healthy Equids: Species Differences and Seasonal Variations"],"prefix":"10.3390","volume":"16","author":[{"given":"Natalia","family":"Siwi\u0144ska","sequence":"first","affiliation":[{"name":"Department of Internal Medicine and Clinic of Diseases of Horses, Dogs and Cats, Wroc\u0142aw University of Environmental and Life Sciences, Grunwaldzki Sq. 47, 50-366 Wroc\u0142aw, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3532-6508","authenticated-orcid":false,"given":"Agnieszka","family":"\u017bak-Bochenek","sequence":"additional","affiliation":[{"name":"Department of Immunology, Pathophysiology and Veterinary Preventive Medicine, Wroc\u0142aw University of Environmental and Life Sciences, 31 Norwida St., 50-375 Wroc\u0142aw, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3141-6722","authenticated-orcid":false,"given":"Paulina","family":"Jawor","sequence":"additional","affiliation":[{"name":"Department of Immunology, Pathophysiology and Veterinary Preventive Medicine, Wroc\u0142aw University of Environmental and Life Sciences, 31 Norwida St., 50-375 Wroc\u0142aw, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0005-0132-4802","authenticated-orcid":false,"given":"Aleksandra","family":"Pietrzak","sequence":"additional","affiliation":[{"name":"Faculty of Veterinary Medicine, Wroc\u0142aw University of Environmental and Life Sciences, 31 Norwida St., 50-375 Wroc\u0142aw, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0009-4152-0989","authenticated-orcid":false,"given":"Oliwia","family":"Kutermak","sequence":"additional","affiliation":[{"name":"Faculty of Veterinary Medicine, Wroc\u0142aw University of Environmental and Life Sciences, 31 Norwida St., 50-375 Wroc\u0142aw, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7014-956X","authenticated-orcid":false,"given":"Malwina","family":"S\u0142owikowska-\u0141o\u015b","sequence":"additional","affiliation":[{"name":"Department of Internal Medicine and Clinic of Diseases of Horses, Dogs and Cats, Wroc\u0142aw University of Environmental and Life Sciences, Grunwaldzki Sq. 47, 50-366 Wroc\u0142aw, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Beata","family":"Kaczmarek","sequence":"additional","affiliation":[{"name":"Department and Clinic of Animal Internal Diseases, University of Life Sciences in Lublin, 15 Akademicka Str., 20-950 Lublin, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,4,7]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"650","DOI":"10.1111\/j.1939-1676.2010.0500.x","article-title":"Seasonal variation in serum concentrations of selected metabolic hormones in horses","volume":"24","author":"Place","year":"2010","journal-title":"J. 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