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Pituitary Pars Intermedia Dysfunction.
Abstract: Pituitary pars intermedia dysfunction (PPID) is one of the most common equine endocrine disorders. It is caused by oxidative damage to dopaminergic neurons in the hypothalamus and results in loss of inhibition of the pituitary pars intermedia. This leads to increased circulating concentrations of adrenocorticotropic hormone (ACTH) and related peptides. Diagnosis is based on increased resting and/or thyrotropin releasing hormone-stimulated ACTH concentrations. Assessment of insulin regulation is also important, as insulin dysregulation occurs in at least one-third of PPID cases and is associated with laminitis risk. Management requires treatment with the dopamine agonist pergolide and an appropriate diet.
Copyright © 2026 Elsevier Inc. All rights reserved.
Publication Date: 2026-09-01 PubMed ID: 42680637DOI: 10.1016/j.cveq.2026.07.012Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
- Review
Summary
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Overview
- Pituitary pars intermedia dysfunction (PPID) is a common hormonal disorder in horses.
- It results from damage to certain neurons in the brain, leading to hormone imbalances.
- Diagnosis involves hormone testing, and management includes medication and diet adjustments.
Background and Cause
- PPID affects the pituitary gland, specifically the pars intermedia region.
- The condition arises due to oxidative damage to dopaminergic neurons located in the hypothalamus.
- Dopaminergic neurons normally inhibit the pituitary pars intermedia, so damage reduces this inhibition.
- Loss of inhibition causes the pituitary to produce excessive amounts of adrenocorticotropic hormone (ACTH) and related peptides.
Pathophysiology and Hormonal Changes
- Increased ACTH levels stimulate the adrenal glands, affecting cortisol production and other hormone pathways.
- This hormonal imbalance can create clinical signs seen in affected horses, such as changes in coat, weight, and metabolism.
Diagnosis
- Diagnosis relies on measuring resting concentrations of ACTH in the blood.
- Additional testing may involve stimulation of ACTH production by administering thyrotropin releasing hormone (TRH), with subsequent ACTH measurement to confirm elevated levels.
- These tests help confirm the dysfunction of the pituitary pars intermedia.
Importance of Insulin Regulation
- At least one-third of horses with PPID also experience insulin dysregulation.
- Insulin dysregulation is clinically important because it is associated with an increased risk of laminitis, a painful and potentially debilitating hoof condition.
- Thus, assessing insulin function is a critical part of managing horses with PPID.
Management and Treatment
- The primary medical treatment for PPID is pergolide, a dopamine agonist that helps restore inhibitory control over the pituitary pars intermedia.
- Appropriate dietary management is essential to support metabolic health and reduce complications.
- Control of insulin levels through diet and possibly additional medications reduces the risk of laminitis.
- Long-term management includes monitoring hormone levels and clinical signs to adjust treatments as needed.
Cite This Article
APA
Vaughn SA, Hart KA.
(2026).
Pituitary Pars Intermedia Dysfunction.
Vet Clin North Am Equine Pract, S0749-0739(26)00059-3.
https://doi.org/10.1016/j.cveq.2026.07.012 Publication
Researcher Affiliations
- Department of Animal and Dairy Science, College of Agricultural and Environmental Sciences, University of Georgia, Athens, GA, USA.
- Department of Large Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens GA, USA. Electronic address: khart4@uga.edu.
Conflict of Interest Statement
Disclosure S.A. Vaughn is a contracted pharmacovigilance veterinarian for Boehringer Ingelheim, the manufacturer of an approved drug to treat equine PPID and is compensated in excess of $5000 annually. K.A. Hart has served as an uncompensated equine endocrinology consultant and has received research gift from Zomedica, Inc., the manufacturer of an equine ACTH assay used for PPID diagnosis, and as a compensated consultant receiving in excess of $5000 annually for Boehringer Ingelheim, the manufacturer of an approved drug to treat equine PPID.
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