Which pattern describes Graves disease in terms of FT4 and TSH?

Which pattern describes Graves disease in terms of FT4 and TSH?

• A. FT4 increased; TSH increased
• B. FT4 increased; TSH decreased
• C. FT4 decreased; TSH decreased
• D. FT4 decreased; TSH increased

Answer: (B)

Graves disease causes hyperthyroidism through antibodies that stimulate the TSH receptor on the thyroid. This drives the gland to pump out more thyroid hormones, so the free thyroxine level (FT4) rises. Because there is now an excess of thyroid hormones in circulation, the pituitary receives negative feedback and reduces TSH production, leading to a low TSH level. Thus the characteristic pattern is FT4 increased with TSH decreased. If FT4 were low, you’d be looking at hypothyroidism; if TSH were high with high FT4, that would suggest a pituitary-origin or TSH-secreting condition, not Graves.