Serum thyroid hormone, insulin, glucose, triglycerides and protein concentrations in normal horses: association with topical dexamethasone usage.

This research paper explores the effects of the topical application of dexamethasone on factors such as thyroid hormones, glucose, triglycerides, protein and insulin levels in horses. The topical use of this drug was found to alter thyroid function and affect metabolic processes, posing potential implications for doping cases in racing horses.

Objective of the Study

• The primary aim of this study was to investigate whether the topical application of dexamethasone affected serum concentrations of thyroid hormones (Triiodothyronine T(3) and Thyroxine T(4)), glucose, triglycerides, total protein, and insulin in normal horses.

Methodology

• A set of ten horses was treated twice daily for a period of ten days with 50g dexamethasone, using an ointment formulation.
• The research employed standard radioimmunoassay methods to assay thyroid hormones and insulin, while glucose, triglycerides, and total protein were determined using standard enzymatic methods and the Biuret reaction.

Findings

• Post-treatment, it was observed that serum glucose and triglyceride concentrations showed an increase, concurrent with a 2 to 6-fold rise in serum insulin levels.
• The total protein concentration in the serum remained unaffected by the treatment.
• Insulin secretion increased with accompanying hyperglycemia and hypertriglyceridemia, while a non-significant decline in T(4) secretion was observed.
• Continuous declines were observed for serum T(3) and T(4) levels, going below the baseline values from the 48-hour mark.
• Three days after treatment was withdrawn, glucose and insulin levels returned to baseline, while triglycerides returned to baseline levels in seven days.
• On the other hand, the baseline serum levels for T(3) and T(4) were not reached even 20 days after the withdrawal of the drug treatment.

Implications

• These findings indicate that the topical administration of dexamethasone impacts the thyroid function and overall physiological metabolic functions in horses.
• This poses potential implications for potential doping cases in racing horses, thus necessitating a thorough understanding and consideration of dexamethasone’s effects.