A patient has decreased total T4 and free T4, positive thyroid peroxidase antibody, and increased TSH. This pattern most likely indicates which condition?

• A. Hyperthyroidism
• B. Hypothyroidism
• C. Normal thyroid
• D. Graves disease

Answer: (B)

When T4 (total and free) is decreased and TSH is increased, it shows the pituitary is trying to stimulate the thyroid because the thyroid isn’t producing enough hormone. That combination points to primary hypothyroidism. The positive thyroid peroxidase antibody supports an autoimmune cause, most commonly Hashimoto thyroiditis, which is a leading cause of hypothyroidism.

If it were Graves disease, you’d expect the opposite pattern—high T4 with suppressed TSH—and if the thyroid were normal, TSH and T4 would both be normal. The autoimmune marker aligns with hypothyroidism due to autoimmune thyroiditis, making hypothyroidism the best fit.