What is the normal reference range for TSH, and what does an elevated level indicate?

What is the normal reference range for TSH, and what does an elevated level indicate?

• A. 0.4–4.0 mIU/L; elevated indicates hypothyroidism
• B. 1–5 mIU/L; elevated indicates hypothyroidism
• C. 0.1–0.5 mIU/L; elevated indicates diabetes
• D. 2–6 mIU/L; elevated indicates anemia

Answer: (A)

TSH is the pituitary signal that tells the thyroid to produce hormones. When thyroid hormone levels are low, the pituitary raises TSH to stimulate the thyroid. So an elevated TSH typically indicates hypothyroidism, specifically primary hypothyroidism where the thyroid isn’t making enough hormones. The usual reference range used in practice and exams is about 0.4–4.0 mIU/L. If TSH is elevated, it points to an underactive thyroid rather than conditions like diabetes or anemia, which involve different parts of the lab workup.

TSH is the pituitary signal that tells the thyroid to produce hormones. When thyroid hormone levels are low, the pituitary raises TSH to stimulate the thyroid. So an elevated TSH typically indicates hypothyroidism, specifically primary hypothyroidism where the thyroid isn’t making enough hormones. The usual reference range used in practice and exams is about 0.4–4.0 mIU/L. If TSH is elevated, it points to an underactive thyroid rather than conditions like diabetes or anemia, which involve different parts of the lab workup.