There are two main causes of high thyroid hormone levels: the first is an autoimmune disease of the thyroid gland disease itself that causes excessive synthesis and secretion of hormones by thyroid cells, which leads to elevated blood thyroid hormones. The second cause is a pituitary lesion that produces too much thyroid hormone by overproducing thyroid stimulating hormones. High thyroid hormone can cause various kinds of harm to the human body, such as increased metabolism, excessive energy consumption, wasting or malnutrition, increased sympathetic excitation, emotional instability, and also prone to cardiovascular disease, whose heart may increase its cardiac output, thus causing increased cardiac load, increased heart rate, increased oxygen consumption, serious arrhythmia, and hyperthyroid heart disease. Therefore, if elevated thyroid hormone levels are found clinically, you need to go to a hospital for detailed examination and then diagnose the cause of the disease. If thyroid function suggests: low TSH levels and high FT3 and FT4 levels, it may be due to primary hyperthyroidism. If the TSH level is high and FT3 and FT4 levels are also high, it may be pituitary hyperthyroidism, and if hypothyroidism is caused by high thyroid hormone due to overdose of eugenol, it is pharmacological hyperthyroidism.