The thyroid hormone (T3 and T4)

Thyroid hormones, mainly T3 (triiodothyronine) and T4 (thyroxine), are chemical messengers produced by the thyroid gland in your neck. They regulate how fast your body's metabolism works, influencing energy levels, body temperature, and overall function. T4 is the more abundant form but less active, while T3 is the active form that impacts cells directly. These hormones help control growth, development, and how your body uses nutrients. Proper levels are essential; too little can cause fatigue and weight gain, while too much may lead to rapid heartbeat and anxiety.