Which screening test is recommended for thyroid disease in symptomatic or high-risk midlife women?

• A. Thyroid ultrasound
• B. Free T4 measurement
• C. Anti-thyroid peroxidase antibodies
• D. TSH testing

Answer: (D)

TSH testing is the best first screen because the pituitary gland is highly sensitive to thyroid hormone levels and adjusts TSH accordingly. A small drop in thyroid hormone often causes a noticeable rise in TSH before Free T4 changes, so TSH detects hypothyroidism early. Conversely, TSH is suppressed early in hyperthyroidism, sometimes even before Free T4 or Free T3 rise. Anti-TPO antibodies indicate autoimmune risk but don’t measure current thyroid function, and thyroid ultrasound assesses structure rather than function, so it isn’t used for routine screening. Therefore, TSH testing best identifies thyroid disease in symptomatic or high-risk midlife women.