What is required for the production of hormones in the thyroid gland for horses?

Iodine is essential for the production of hormones in the thyroid gland of horses, as well as in other animals including humans. The thyroid gland synthesizes hormones, primarily thyroxine (T4) and triiodothyronine (T3), which are critical for regulating metabolism, growth, and development. Iodine serves as a necessary building block in the formation of these hormones. Without sufficient iodine, the synthesis of T3 and T4 can be impaired, which can lead to conditions such as hypothyroidism and goiter in horses.

The other substances listed—sodium, chloride, and selenium—play different roles in the body but are not directly involved in the production of thyroid hormones. Sodium and chloride are primarily associated with fluid balance and nerve function, while selenium is important for other functions, including antioxidant defense and immune response, but it does not directly influence thyroid hormone production. Understanding the specific roles of these nutrients helps emphasize the importance of iodine in maintaining healthy thyroid function in horses.