What is the normal range for TSH in hypothyroidism?

Generally, “hypothyroidism” refers to decreased thyroid function. Hypothyroidism is a metabolic disorder caused by reduced synthesis and secretion of thyroid hormones or insufficient physiological effects of these hormones. In hypothyroidism, the serum TSH (thyroid-stimulating hormone) level typically ranges from 0.5 to 3.0 mIU/L. A detailed explanation follows:

TSH is secreted by the pituitary gland and functions to stimulate the thyroid gland to synthesize and secrete thyroid hormones. In hypothyroidism, diminished thyroid hormone production fails to exert adequate negative feedback inhibition on the pituitary gland, resulting in elevated TSH levels. Conversely, in hyperthyroidism, TSH levels decrease.

In patients with hypothyroidism, an elevated TSH level above the normal reference range indicates inadequate thyroid function, necessitating thyroid hormone replacement therapy—commonly with levothyroxine sodium tablets. Regular monitoring of TSH is essential to maintain it within the target therapeutic range, generally 0.5–3.0 mIU/L. If TSH remains persistently outside this range, the medication dose should be adjusted to prevent adverse effects on cardiac function, lipid metabolism, and other systems.

Patients with hypothyroidism require regular TSH testing and individualized management to maintain TSH within an appropriate, clinically optimized range. During treatment, patients must strictly adhere to their physician’s instructions—neither discontinuing medication nor altering the dose without medical guidance—and should promptly consult their healthcare provider for evaluation and adjustment of the treatment plan if any adverse symptoms arise.