Urinary cortisol:creatinine ratios in healthy horses and horses with hyperadrenocorticism and non-adrenal disease.

The research article explores the differences in urinary cortisol and creatinine levels, and their ratios, among healthy horses, horses with Cushing’s disease, and horses suffering from dysautonomia syndrome (equine grass sickness). The findings suggest that a certain threshold in the cortisol:creatinine ratio can aid in diagnosing Cushing’s disease.

Overview and Methodology

• The study examined urinary cortisol and creatinine concentrations and the cortisol:creatinine ratio in three groups of horses – healthy horses (Group 1), horses with Cushing’s disease (Group 2), and horses with dysautonomia syndrome, also known as equine grass sickness (Group 3).
• In total, researchers collected data from twelve healthy horses, thirteen horses with Cushing’s disease, and eight horses with dysautonomia syndrome. These different conditions were selected for study because of their varied impacts on the horse’s adrenal glands.

Findings

• The average urinary cortisol concentrations and creatinine concentrations varied between the three groups. Group 3 (horses with dysautonomia syndrome) exhibited significantly higher urinary cortisol and creatinine concentrations compared to the other two groups.
• However, there was no significant difference between the cortisol:creatinine ratios among the three groups, although there was a trend towards higher values in groups with disease conditions (Groups 2 and 3).

Implications for Diagnosis of Cushing’s Disease

• A diagnostic cut-off in the cortisol:creatinine ratio was proposed for confirming Cushing’s disease. A ratio of more than 6.9 x 10(-6) was associated with a diagnostic sensitivity of 92.3% and a specificity of 75.0% when compared to healthy horses.
• However, when the dysautonomia syndrome horses were included in the comparison, a cortisol:creatinine ratio of more than 7.4 x 10(-6) offered a lower diagnostic sensitivity (84.6%) and specificity (54.5%).
• This research suggests that measuring the cortisol:creatinine ratio in horse urine may be a useful tool for diagnosing Cushing’s disease, but the presence of other illnesses like dysautonomia syndrome could complicate the assessment.