Journal of veterinary internal medicine2026; 40(4); aalag182; doi: 10.1093/jvimsj/aalag182

Preliminary evaluation of beta-endorphin alone and in combination with adrenocorticotropic hormone for the diagnosis of pituitary pars intermedia dysfunction in equids.

Billmann, P
·
Durham, AE
·
Christen, G
·
Gerber, V
·
Gross, J
·
Fouché, N

Abstract: Limited published data exist regarding the diagnostic utility of beta-endorphin (β-END) for pituitary pars intermedia dysfunction (PPID), either compared with or in combination with adrenocorticotropic hormone (ACTH). Objective: To evaluate β-END as a potential diagnostic test for PPID in comparison with ACTH and to explore the diagnostic performance of combined tests. Methods: Ninety-eight equids aged 19-32 years, owned by the foundation "Stiftung für das Pferd," were included. Methods: A cross-sectional study was conducted in January 2025. Haircoat abnormalities were scored as absent, mild, or pronounced, and plasma β-END and ACTH concentrations were measured. Horses were classified based on haircoat abnormalities, with pronounced haircoat abnormalities defining the PPID group (n = 39) and absence of haircoat abnormalities defining the control group (n = 59). Receiver-operating characteristic (ROC) analyses were performed for individual and combined diagnostic tests. Previously established ACTH cut-offs were combined with study-derived maximum Youden-Index cut-offs. Results: Beta-endorphin showed an area under the ROC curve (AUROC) of 0.88 for PPID diagnosis, with a sensitivity of 76.9% and specificity of 93.2%. Corresponding AUROCs, sensitivities, and specificities were 0.87, 71.8%, and 88.1% for ACTH measured by chemiluminescent assay (CLA), and 0.83, 79.5%, and 69.5% for ACTH measured by immunofluorescent assay (IFA). Combining β-END at 115 pg/mL with ACTH (CLA) at 24.3 pg/mL yielded 88% sensitivity and 89% specificity. Conclusions: These preliminary findings support further evaluation of β-END as an adjunct diagnostic test for PPID.

Get Full Text

Publication Date: 2026-08-21 PubMed ID: 42627935PubMed Central: PMC13496237DOI: 10.1093/jvimsj/aalag182Google 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.

Facebook X LinkedIn Email Copy

Summary
Cite This
Publication
Affiliations
MeSH
Grants
Conflict of Interest
References
Citations

Journal Article

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

Overview

This study evaluated the effectiveness of beta-endorphin (β-END), alone and combined with adrenocorticotropic hormone (ACTH), as diagnostic tools for pituitary pars intermedia dysfunction (PPID) in horses.
The researchers compared the diagnostic performance of β-END with ACTH and investigated whether combining these tests improves PPID diagnosis accuracy.

Background

PPID, also known as equine Cushing’s disease, is a common endocrine disorder in older horses, often identified by clinical signs such as abnormal haircoat.
ACTH measurement is a standard diagnostic test for PPID but has limitations related to assay type and sensitivity.
Beta-endorphin (β-END), a neuropeptide, may have potential as a diagnostic biomarker for PPID but lacks extensive research regarding its clinical utility.

Study Objective

To evaluate the diagnostic utility of plasma β-END concentration for PPID.
To compare β-END’s diagnostic performance directly with two types of ACTH assays: chemiluminescent assay (CLA) and immunofluorescent assay (IFA).
To investigate whether combining β-END levels with ACTH measurements enhances diagnostic sensitivity and specificity.

Methods

Subjects: 98 aged horses (19-32 years) from a foundation called “Stiftung für das Pferd”.
Classification:
- PPID group: 39 horses showing pronounced haircoat abnormalities.
- Control group: 59 horses with no haircoat abnormalities.
Data collected:
- Haircoat condition scored as absent, mild, or pronounced.
- Blood samples to measure plasma β-END and ACTH concentrations.
Diagnostic tests comparison:
- ACTH was measured using two assays: chemiluminescent assay (CLA) and immunofluorescent assay (IFA).
- Receiver-operating characteristic (ROC) curve analysis was performed for β-END alone, ACTH assays alone, and combined tests.
- Cut-off values to separate PPID and control groups were determined using previously known ACTH thresholds along with new cut-offs derived by maximizing the Youden Index from study data.

Results

Beta-endorphin alone had good diagnostic performance:
- Area Under the ROC Curve (AUROC): 0.88 (close to excellent discrimination).
- Sensitivity: 76.9% (correctly identifies about 77% of PPID cases).
- Specificity: 93.2% (correctly excludes about 93% of non-PPID cases).
ACTH measured by CLA assay:
- AUROC: 0.87 (very similar to β-END).
- Sensitivity: 71.8% (slightly lower than β-END).
- Specificity: 88.1% (slightly lower than β-END).
ACTH measured by IFA assay:
- AUROC: 0.83 (lower than β-END and ACTH CLA).
- Sensitivity: 79.5% (slightly higher than ACTH CLA and β-END alone).
- Specificity: 69.5% (lower than other methods, indicating more false positives).
Combination of tests:
- Using β-END cut-off at 115 pg/mL combined with ACTH CLA cut-off at 24.3 pg/mL.
- Achieved 88% sensitivity and 89% specificity.
- This combination improved the accuracy of PPID diagnosis compared to individual tests.

Conclusions and Implications

Beta-endorphin shows promise as a diagnostic biomarker for PPID with performance comparable to or better than some ACTH assays.
Combining β-END with ACTH measurement enhances diagnostic accuracy, suggesting a complementary approach.
This preliminary data supports further research to validate β-END in larger, possibly more diverse equine populations.
Improved diagnostic protocols may lead to earlier and more accurate detection of PPID, enabling better management of affected horses.

Cite This Article

APA

Billmann P, Durham AE, Christen G, Gerber V, Gross J, Fouché N. (2026). Preliminary evaluation of beta-endorphin alone and in combination with adrenocorticotropic hormone for the diagnosis of pituitary pars intermedia dysfunction in equids. J Vet Intern Med, 40(4), aalag182. https://doi.org/10.1093/jvimsj/aalag182

Publication

Journal of veterinary internal medicine

ISSN: 1939-1676

NlmUniqueID: 8708660

Country: England

Language: English

Volume: 40

Issue: 4

PII: aalag182

Researcher Affiliations

Billmann, Paula

Swiss Institute of Equine Medicine, Vetsuisse Faculty, University of Bern, Bern, Switzerland.

Durham, Andy E

The Liphook Equine Hospital, Liphook, Hampshire, GU30 7JG, United Kingdom.

Christen, Garance

Swiss Institute of Equine Medicine, Vetsuisse Faculty, University of Bern, Bern, Switzerland.

Gerber, Vinzenz

Swiss Institute of Equine Medicine, Vetsuisse Faculty, University of Bern, Bern, Switzerland.

Gross, Josef

Veterinary Physiology, Vetsuisse Faculty, University of Bern, Bern, Switzerland.

Fouché, Nathalie

Swiss Institute of Equine Medicine, Vetsuisse Faculty, University of Bern, Bern, Switzerland.

MeSH Terms

Animals
Adrenocorticotropic Hormone / blood
Horses
beta-Endorphin / blood
Horse Diseases / diagnosis
Horse Diseases / blood
Pituitary Gland, Intermediate / physiopathology
Pituitary Diseases / veterinary
Pituitary Diseases / diagnosis
Pituitary Diseases / blood
Female
Male
Cross-Sectional Studies
Sensitivity and Specificity

Grant Funding

Faculty Clinical Research Platform (FCRP) of the Vetsuisse Faculty, University of Bern
1315/2024 / Vontobel Foundation
33-890 / Internal Research Fund of the Swiss Institute of Equine Medicine, Bern, Switzerland

Conflict of Interest Statement

A.D. is employed by Liphook Equine Hospital, which offers commercial equine laboratory services for quantification of adrenocorticotropic hormone (ACTH) concentrations.