Association between insulin dysregulation and adrenocorticotropic hormone in aged horses and ponies with no clinical signs of pituitary pars intermedia dysfunction.
Authors: Li Fang I, Spence Robert J, de Laat Melody A, Harris Patricia A, Sonntag Johanna, Menzies-Gow Nicola J, Durham Andy E, Bailey Simon R, Sillence Martin N
Journal: Equine veterinary journal
Summary
# Editorial Summary Elevated ACTH is the cornerstone of pituitary pars intermedia dysfunction (PPID) diagnosis in older horses, yet the hormone's complexity means clinicians must understand all variables affecting its concentration before confidently interpreting results. This 2023 study investigated whether insulin dysregulation—a condition increasingly recognised in aged equines—independently influences ACTH levels, since insulin is known to modulate pituitary function in other mammalian species. The researchers examined aged horses and ponies without clinical PPID signs, stratifying them by insulin status to isolate the relationship between insulin dysregulation and ACTH concentration. They found a significant positive association between insulin dysregulation and elevated ACTH, suggesting that insulin status influences circulating ACTH independently of PPID pathology. These findings carry important diagnostic implications: when interpreting ACTH results in older animals, particularly those with concurrent insulin dysregulation, practitioners should recognise that elevated ACTH may not exclusively indicate pituitary disease, and establishing more refined diagnostic thresholds that account for metabolic status could improve diagnostic specificity and reduce false positives for PPID.
Read the full abstract on PubMed
Practical Takeaways
- •ACTH alone should not be used as a sole diagnostic indicator for PPID; insulin status and dysregulation must be evaluated concurrently for accurate diagnosis
- •Aged horses and ponies with elevated ACTH but no clinical PPID signs may have insulin dysregulation as a confounding factor, requiring comprehensive endocrine assessment
- •Request both insulin and ACTH testing in aged animals with metabolic concerns to differentiate between primary PPID and secondary ACTH elevation from insulin dysregulation
Key Findings
- •Insulin dysregulation may influence ACTH concentrations independently of PPID in aged horses and ponies
- •High ACTH concentrations are not specific to PPID and other factors must be considered when interpreting diagnostic reference ranges
- •Understanding the relationship between insulin dysregulation and ACTH is necessary to improve diagnostic confidence for PPID detection