What are considered normal TSH levels?

Normal thyroid-stimulating hormone (TSH) levels are typically considered to be within the range of 0.4 to 4.0 micro-international units per milliliter (µIU/mL). TSH is a hormone produced by the pituitary gland that stimulates the thyroid gland to release thyroid hormones (T3 and T4), which are crucial for metabolism and energy regulation in the body.

The reference range of 0.4 to 4.0 µIU/mL indicates that when a person's TSH levels fall within this range, it is usually associated with normal thyroid function. TSH levels outside of this range may indicate thyroid dysfunction—either hypothyroidism (underactive thyroid) if TSH levels are elevated or hyperthyroidism (overactive thyroid) if TSH levels are low.

Understanding these normal ranges helps healthcare providers interpret thyroid function tests accurately and make appropriate clinical decisions regarding diagnosis and treatment.