Pituitary pars intermedia dysfunction: equine Cushing’s disease.
Abstract: PPID in older equids has become a major health concern of horse owners. In response, equine practitioners have made greater efforts at understanding, diagnosing, and treating this disorder. Although PPID is recognized to be a different form of pituitary-dependent hyperadrenocorticism than is seen in canine or human patients, relatively little is known about the pathophysiology and natural progression of the disease. At present, the diagnosis is best supported by manifestation of characteristic clinical signs and endocrinologic test results, preferably a supportive DST result. Treatment must focus on improving overall health care, including body clipping, dentistry, and nutrition. As the condition progresses, administration of pergolide or a combination of pergolide and cyproheptadine is currently considered the best medical treatment. The time point at which medication should be added to improved health care and management changes is not currently known, but loss of body condition and development of hyperglycemia suggest more advanced PPID that would likely benefit from drug therapy. Whether medical treatment needs to be continuous or could be intermittent is also unknown. As the demand for treatment of affected equids continues to increase, clinical response and endocrinologic testing data as well as pharmacologic data for currently used drugs and other agents should be expected. Similarly, novel medical, and perhaps surgical, treatment strategies for this condition should also be anticipated in the future.
Publication Date: 2005-01-08 PubMed ID: 15635907DOI: 10.1016/s0749-0739(02)00018-4Google Scholar: Lookup
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Summary
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This research article discusses the increasing prevalence of Pituitary Pars Intermedia Dysfunction (PPID), or equine Cushing’s disease, in older horses and highlights current understanding, diagnosis, and treatment strategies. The study also emphasizes the need for more research to explore novel medical and surgical treatments for this condition.
Understanding PPID
- The Pituitary Pars Intermedia Dysfunction (PPID) is a health problem often found in older horses which has raised serious concerns among horse owners.
- While PPID is known to be a different form of pituitary-dependent hyperadrenocorticism than observed in dogs or human patients, the pathophysiology and natural progression of the disease are not yet fully understood.
Diagnosis
- The diagnosis of PPID is largely dependent on identifying typical clinical signs and confirming through endocrinologic test results, with preference given to a supportive DST (Dexamethasone Suppression Test) result.
- There isn’t enough knowledge yet to identify when in the progression of the disease medication should be introduced in addition to improved healthcare and management changes.
- Signs like loss of body condition and development of hyperglycemia indicate a severity of PPID that would likely benefit from drug treatment.
Treatment strategies
- The focus of the treatment should be on overall healthcare improvement which includes body clipping, proper dental care, and nutrition.
- Pergolide administration or a combination of pergolide and cyproheptadine is currently viewed as the best medical treatment.
- Questions remain on whether the medical treatment needs to be ongoing or could be intermittent.
Further Research
- With a climbing demand for treatment for PPID, it is anticipated that further clinical, endocrinologic testing, and pharmacologic data will be produced.
- Furthermore, the development of newer medical or surgical treatments for PPID could be expected in the future as our understanding of the fundamental science improves.
Cite This Article
APA
Schott HC.
(2005).
Pituitary pars intermedia dysfunction: equine Cushing’s disease.
Vet Clin North Am Equine Pract, 18(2), 237-270.
https://doi.org/10.1016/s0749-0739(02)00018-4 Publication
Researcher Affiliations
- Department of Large Animal Clinical Sciences, D-202 Veterinary Medical Center, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824-1314, USA. schott@cvm.msu.edu
MeSH Terms
- Adrenocorticotropic Hormone / metabolism
- Animals
- Dexamethasone
- Dopamine Agonists / therapeutic use
- Female
- Horse Diseases / diagnosis
- Horse Diseases / drug therapy
- Horse Diseases / pathology
- Horses
- Hydrocortisone / blood
- Male
- Pergolide / therapeutic use
- Pituitary ACTH Hypersecretion / diagnosis
- Pituitary ACTH Hypersecretion / drug therapy
- Pituitary ACTH Hypersecretion / veterinary
- Pituitary Gland / anatomy & histology
- Pituitary Gland / metabolism
- Pituitary Gland / pathology
- Treatment Outcome
Citations
This article has been cited 19 times.- Kirkwood NC, Hughes KJ, Stewart AJ. Prospective Case Series of Clinical Signs and Adrenocorticotrophin (ACTH) Concentrations in Seven Horses Transitioning to Pituitary Pars Intermedia Dysfunction (PPID). Vet Sci 2022 Oct 17;9(10).
- Kirkwood NC, Hughes KJ, Stewart AJ. Pituitary Pars Intermedia Dysfunction (PPID) in Horses. Vet Sci 2022 Oct 10;9(10).
- Nitzsche AM, Fey K, Büttner K, Gröf M, Staszyk C. The Gingiva of Horses With Pituitary Pars Intermedia Dysfunction: A Macroscopic Anatomical Evaluation. Front Vet Sci 2021;8:786971.
- Thane K, Uricchio C, Frank N. Effect of early or late blood sampling on thyrotropin releasing hormone stimulation test results in horses. J Vet Intern Med 2022 Mar;36(2):770-777.
- Gehlen H, Fisch J, Merle R, Trachsel DS. Preliminary study on the effects of pergolide on left ventricular function in the horses with pituitary pars intermedia dysfunction. J Vet Sci 2021 Sep;22(5):e64.
- Fortin JS, Hetak AA, Duggan KE, Burglass CM, Penticoff HB, Schott HC 2nd. Equine pituitary pars intermedia dysfunction: a spontaneous model of synucleinopathy. Sci Rep 2021 Aug 6;11(1):16036.
- Tsuchiya T, Noda R, Ikeda H, Maeda M, Sato F. Relationship between endogenous plasma adrenocorticotropic hormone concentration and reproductive performance in Thoroughbred broodmares. J Vet Intern Med 2021 Jul;35(4):2002-2008.
- Tatum RC, McGowan CM, Dean RS, Ireland JL. Equine pituitary pars intermedia dysfunction: Identifying research priorities for diagnosis, treatment and prognosis through a priority setting partnership. PLoS One 2021;16(1):e0244784.
- Horn R, Stewart AJ, Jackson KV, Dryburgh EL, Medina-Torres CE, Bertin FR. Clinical implications of using adrenocorticotropic hormone diagnostic cutoffs or reference intervals to diagnose pituitary pars intermedia dysfunction in mature horses. J Vet Intern Med 2021 Jan;35(1):560-570.
- Fortin JS, Benskey MJ, Lookingland KJ, Patterson JS, Howey EB, Goudreau JL, Schott HC 2nd. Restoring pars intermedia dopamine concentrations and tyrosine hydroxylase expression levels with pergolide: evidence from horses with pituitary pars intermedia dysfunction. BMC Vet Res 2020 Sep 25;16(1):356.
- Horn R, Bertin FR. Evaluation of combined testing to simultaneously diagnose pituitary pars intermedia dysfunction and insulin dysregulation in horses. J Vet Intern Med 2019 Sep;33(5):2249-2256.
- Pijnacker T, Knies M, Galac S, Sanders K, Mol JA, Kooistra HS. TRH-induced secretion of adrenocorticotropin and cortisol in dogs with pituitary-dependent hypercortisolism. Vet Q 2018 Dec;38(1):72-78.
- Spelta CW. Equine pituitary pars intermedia dysfunction: current perspectives on diagnosis and management. Vet Med (Auckl) 2015;6:293-300.
- Carmalt JL, Waldner CL, Allen AL. Equine pituitary pars intermedia dysfunction: An international survey of veterinarians' approach to diagnosis, management, and estimated prevalence. Can J Vet Res 2017 Oct;81(4):261-269.
- Haritou SJ, Zylstra R, Ralli C, Turner S, Tortonese DJ. Seasonal changes in circadian peripheral plasma concentrations of melatonin, serotonin, dopamine and cortisol in aged horses with Cushing's disease under natural photoperiod. J Neuroendocrinol 2008 Aug;20(8):988-96.
- Massardi E, Gaudenzi G, Carra S, Oldani M, Rybinska I, Persani L, Vitale G. Cushing's Disease in the Animal Kingdom: Translational Insights for Human Medicine. Int J Mol Sci 2025 Sep 4;26(17).
- Schott HC 2nd, Strachota JR, Marteniuk JV, Refsal KR. Long-Term Response of Equids With Pituitary Pars Intermedia Dysfunction to Treatment With Pergolide. J Vet Intern Med 2025 May-Jun;39(3):e70109.
- Williams ZJ, Pezzanite LM, Hendrickson DA. Review of skin grafting in equine wounds: indications and techniques. Equine Vet Educ 2024 Sep;36(9):484-493.
- Sundra T, Kelty E, Rossi G, Rendle D. Retrospective assessment of the use of extended-release cabergoline in the management of equine pituitary pars intermedia dysfunction. Front Vet Sci 2024;11:1332337.
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