What is considered the best screening test for hypothyroidism?

The best screening test for hypothyroidism is TSH, or Thyroid-Stimulating Hormone. This hormone is produced by the pituitary gland and plays a crucial role in regulating thyroid function. When the thyroid gland is underactive or not producing enough thyroid hormones (like T4 and T3), the pituitary gland responds by increasing TSH production in an attempt to stimulate the thyroid.

As a screening tool, measuring TSH levels is highly sensitive for detecting hypothyroidism. In fact, an elevated TSH level typically indicates that the thyroid is not producing adequate amounts of hormones. Because TSH levels can provide a clear indication of thyroid function, it is the preferred initial test when evaluating suspected cases of hypothyroidism.

Other tests, such as Free T4, Total T3, and thyroid scans, have different roles in the assessment of thyroid function but are not recommended as first-line screenings. Free T4, for instance, measures the active form of thyroxine in the blood, but it can be affected by various factors and does not provide an early indication of thyroid dysfunction as effectively as TSH. Total T3 is often used to assess hyperthyroidism or in cases of thyroid hormone replacement therapy, while thyroid scans help to