Effects of oral administration of levothyroxine sodium on concentrations of plasma lipids, concentration and composition of very-low-density lipoproteins, and glucose dynamics in healthy adult mares.

This research study examines the effect of levothyroxine sodium on glucose and lipid metabolism in healthy adult horses. It found that administration of this compound reduced blood lipid concentrations, improved insulin sensitivity, and increased insulin disposal, suggesting its potential as a treatment for horses with reduced insulin sensitivity.

Methodology of the Research

• In the study, 12 healthy adult mares were used as the subjects. Eight of these horses were given an incrementally increasing dosage of levothyroxine sodium (24, 48, 72, or 96 mg per day) for 8 weeks.
• The medication was given between 7 AM and 8 AM in their morning grain meal for 2 weeks. The other four horses were not given any treatment and served as controls.
• The researchers measured levels of various parameters such as nonesterified fatty acids, triglyceride, total cholesterol, and very-low-density lipoprotein in blood samples taken between 8 AM and 9 AM at weeks 0, 2, 4, 6, and 8.
• A combined Intravenous Glucose-Insulin Tolerance Test (IVGITT) was performed before and at the end of the treatment period to assess the horses’ glucose dynamics. This data was then interpreted using a minimal model.

Results of the Study

• The results showed that the plasma concentrations of triglyceride, total cholesterol, and very-low-density lipoprotein significantly decreased over time in horses who received the levothyroxine sodium treatment. The mean plasma concentration of very-low-density lipoprotein decreased by more than half from the baseline value at the end of the treatment period.
• Insulin sensitivity of the treated horses significantly improved, being more than two times greater than the initial value. This means that the horses became more efficient at regulating their blood sugar levels after the treatment. However, the glucose effectiveness and net insulin response were not affected.
• The rate of insulin disposal, which is how quickly insulin is removed from the body, significantly increased.

Conclusions of the Research

• Based on these outcomes, the study concluded that the administration of levothyroxine sodium decreases blood lipid concentrations, improves insulin sensitivity, and increases the rate of insulin disposal in horses.
• This suggests that levothyroxine sodium can potentially be used as a treatment for horses with decreased insulin sensitivity. However, further studies are required to strengthen this hypothesis and describe the exact mechanisms involved.