Final answer:
The single best screen test for hypothyroidism is the measurement of Thyroid-Stimulating Hormone (TSH) levels, which is highly sensitive for detecting the disease before symptoms become apparent. Other thyroid hormones may also be measured to confirm the diagnosis.
Step-by-step explanation:
The single best screen test for hypothyroidism is the measurement of Thyroid-Stimulating Hormone (TSH) levels. TSH is a hormone produced by the pituitary gland that regulates the production of thyroid hormones. When thyroid function is low, the pituitary gland will try to stimulate the thyroid by releasing more TSH.
Therefore, a high TSH level is typically indicative of hypothyroidism. Additionally, to confirm the diagnosis of hypothyroidism, levels of thyroid hormones, including Thyroxine (T4) and triiodothyronine (T3), may be tested. TSH is the most sensitive test for hypothyroidism, and it can diagnose the condition even before the symptoms become obvious. Symptoms of hypothyroidism might include fatigue, weight gain, cold sensitivity, constipation, and a low heart rate.
In cases of Hashimoto thyroiditis, which is the most common cause of hypothyroidism in the United States, patients may also develop a goiter along with other symptoms of hypothyroidism. It is important to note that while nuclear imaging, such as thyroid scans with iodine isotopes, can be informative in the assessment of thyroid function, these are generally not first-line tests for hypothyroidism.