What is the primary method used to assess thyroid function?

The primary method used to assess thyroid function is the measurement of thyroid-stimulating hormone (TSH) levels. TSH is produced by the pituitary gland and plays a crucial role in regulating the thyroid gland. When thyroid hormone levels (T3 and T4) are low, TSH secretion increases to stimulate the thyroid to produce more hormones. Conversely, high levels of thyroid hormones lead to decreased TSH production. Therefore, measuring TSH levels provides important insights into thyroid health.

TSH testing is often the first-line screening test for thyroid dysfunction because it is sensitive to changes in thyroid hormone levels. An elevated TSH level typically indicates hypothyroidism, while a suppressed TSH level suggests hyperthyroidism. Thus, TSH measurement serves as a vital indicator for both diagnosing and managing thyroid disorders.