What is a result of increased levels of thyroid hormones T3 and T4?

Increased levels of thyroid hormones T3 (triiodothyronine) and T4 (thyroxine) are directly related to the regulation of metabolism in the body. These hormones play a crucial role in controlling the metabolic rate, which refers to how quickly the body converts food into energy. When the levels of T3 and T4 increase, they stimulate various metabolic processes, leading to an enhanced metabolic rate. This can result in greater energy production, increased calorie expenditure, and potentially weight loss if caloric intake is not adjusted accordingly.

In contrast, decreased metabolism would occur under low levels of these hormones, which can lead to weight gain and decreased energy levels. Constant fatigue is often linked with low thyroid hormone levels, as a slow metabolism can reduce the body's energy levels. Similarly, weight loss resistance is typically a symptom seen in cases of hypothyroidism, where insufficient thyroid hormone availability impedes weight loss efforts. Thus, the result of increased levels of thyroid hormones T3 and T4 being an increased metabolism is well founded within the context of how these hormones function in the endocrine system.