# Copeptin Hormone Concentrations in Dogs with Heart Disease and Relationship with Antidiuretic Hormone

## TL;DR

This study investigates copeptin as a potential biomarker for antidiuretic hormone in dogs with heart disease but finds it does not reliably reflect ADH levels.

## Contribution

The study evaluates copeptin as a practical alternative to ADH measurement in dogs with cardiac disease and finds it does not correlate well.

## Key findings

- Copeptin concentrations did not differ significantly between healthy and diseased dogs.
- Copeptin concentrations did not correlate well with ADH concentrations.
- Copeptin levels were inversely associated with age after controlling for other variables.

## Abstract

Antidiuretic hormone (ADH) plays a crucial role in regulating water balance in dogs, particularly those with heart disease, where its levels are often elevated. However, measuring ADH in a clinical setting can be challenging. This study explored the potential of copeptin, a substance released alongside ADH, as a more practical biomarker for assessing ADH concentrations in dogs with cardiac issues. We examined 59 dogs divided into three groups: healthy dogs, those in the early stages of heart disease, and dogs with congestive heart failure (CHF). Copeptin concentrations were measured and compared across the groups. Our findings revealed no significant differences in copeptin concentrations among the groups. Additionally, we found that copeptin concentrations did not correlate well with ADH concentrations, suggesting that copeptin may not serve as a direct substitute for measuring ADH with the currently available assays. However, copeptin concentrations were influenced by age after controlling for potential explanatory variables, with an inverse relationship. Overall, while lower copeptin concentrations were associated with increasing age, copeptin does not effectively reflect ADH concentrations in dogs with cardiac disease, highlighting the need for further research in this area.

Antidiuretic hormone (ADH) is upregulated in dogs with cardiac disease. However, measurement of ADH is impractical in a clinical setting. Copeptin is co-secreted with ADH, making it a potential biomarker of ADH secretion. We hypothesized that dogs with cardiac disease would upregulate copeptin concentrations and that copeptin would positively correlate with ADH, serum chloride ([Cl−]), and degree of mathematical [Cl−] correction. The study population comprised 19 healthy, 20 preclinical (Stage B), and 20 congestive heart failure (CHF, Stage C or D) dogs. Groups were compared with Kruskal–Wallis tests. The agreement between ADH and copeptin was assessed with Bland–Altman analysis. Relationships between copeptin and clinical variables were explored using multivariable linear regression. There were no significant differences in copeptin concentrations among healthy (median 54.9 pg/mL; range 0.5–196.1), preclinical (median 43.6 pg/mL; range 0.5–131.4), and CHF (median 60.5 pg/mL; range 0.5–997.8) dogs (p = 0.76). Relative to ADH, copeptin showed a negative proportional bias of −87.8 pg/mL with wide limits of agreement (−421.8 to 246.2). Linear regression showed a significant influence of age on copeptin concentration. Copeptin measured by ELISA does not reflect the ADH concentration in healthy dogs or in dogs with cardiac disease. Copeptin concentrations are, however, inversely associated with age.