Which test is primarily used to diagnose hypothyroidism?

The primary test used to diagnose hypothyroidism is the Thyroid-stimulating hormone (TSH) test because it specifically evaluates how well the pituitary gland is functioning, which in turn provides information about the thyroid gland's function. In hypothyroidism, the thyroid does not produce sufficient hormones, leading to an increase in TSH levels as the body attempts to stimulate the thyroid. Therefore, measuring TSH levels can help determine whether there is an underactive thyroid.

While a Complete Blood Count (CBC), an Electrolyte Panel, and a Comprehensive Metabolic Panel might provide valuable insights into a patient’s overall health or other conditions, they do not directly assess thyroid function. The TSH test is specifically designed to evaluate thyroid activity, making it the most appropriate choice for diagnosing hypothyroidism.