Patients often ask: “Do I need a high iodine diet for thyroid disease?” To answer this question, we must first understand the physiological functions of the thyroid gland and the distribution and metabolism of iodine in the body. The thyroid gland is the largest endocrine gland in the human body, in the shape of a butterfly, located in the lower part of the neck, and plays a very important role in regulating the physiological metabolism of the human body, maintaining the normal function of the organs and tissues of the body’s systems and enabling the body to live and work normally. Its physiology includes the effects on various aspects such as thermogenesis, protein metabolism, fat metabolism, sugar metabolism, vitamin metabolism, water and salt metabolism, and neuromuscular system. If there is an excess or deficiency of thyroid hormones secreted by the thyroid tissue, it has a huge impact on the body’s functions, especially energy levels. Iodine is an essential trace element that is taken up mainly from food. After entering the body, iodine is taken up and concentrated by the thyroid gland, so the iodine content in the thyroid gland is about 40 times higher than in the blood, accounting for 70-80% of the total amount of iodine in the body. 90% of the iodine is excreted in the urine and stored in the body for 2-3 months. Iodine is the raw material for the body’s synthesis of thyroid hormones and mainly regulates the function and volume of the thyroid gland. When iodine intake is deficient, thyroid hormone synthesis decreases and thyroid hormone levels in the blood drop, which feeds back to the pituitary gland causing increased secretion of thyrotropic hormone (TSH) and compensatory stimulation of the thyroid gland to produce hormones that maintain normal thyroid function and increase the size of the thyroid gland. When iodine is severely deficient, its compensatory capacity is diminished and hypothyroidism occurs. With excessive iodine intake, iodine in the thyroid gland increases significantly, interfering with the iodination of tyrosine, affecting the synthesis of thyroid hormones, and increasing the secretion of feedback TSH, causing an enlarged thyroid gland with normal compensatory thyroid function. A large amount of iodine enters the body, thyroid hormone synthesis and secretion decreases, and persistent inhibition of thyroid hormone secretion into the bloodstream occurs with methacholine. If the self-regulatory function is impaired, thyroid hormone secretion into the bloodstream is sustained and hyperthyroidism occurs. In addition, it can increase the incidence of autoimmune thyroid diseases, such as Hashimoto’s thyroiditis and Graves’ disease. In summary, the link between iodine intake and goiter and dysfunction is a U-shaped relationship, meaning that too much or too little iodine intake can lead to an increase in thyroid disorders. With the introduction of salt iodization worldwide, the iodine intake of the global population has increased significantly, and with it, iodine overdose has gradually emerged. Shanghai and the coastal area are not iodine deficient areas, so as long as residents eat normally and do not picky eaters, iodine deficiency will not occur and there is no need to intentionally eat a high iodine diet. For patients with thyroid disease, excessive iodine intake will not only aggravate the disease, but also prolong its course, so diet and medication should be administered under the guidance of an endocrinologist. Traditional Chinese medicine has its unique advantages in the treatment of thyroid disease, but care should be taken to avoid the use of certain algae, kelp, shells, ores and other phlegm-softening drugs that are high in iodine in the treatment of medication to prevent changes in the condition.