Which pattern best describes primary hyperthyroidism in terms of TSH, FT4, TT3/TT4, and T3 uptake?

• A. TSH low; FT4 high; TT3/TT4 high; T3 uptake high
• B. TSH high; FT4 low; TT3/TT4 low; T3 uptake low
• C. TSH high; FT4 high; TT3/TT4 high; T3 uptake high
• D. TSH normal; FT4 normal; TT3/TT4 normal; T3 uptake normal

Answer: (C)

In primary hyperthyroidism the thyroid overproduces hormones, so the pituitary senses the excess and reduces TSH through negative feedback. That makes TSH fall (low). The circulating free hormone (FT4) rises, and total thyroid hormones (TT3/TT4) are typically elevated as well. The T3 uptake test tends to be higher in hyperthyroidism because it reflects the higher level of circulating thyroid hormone affecting binding sites in the assay.

So the pattern you’d expect is low TSH with high FT4, high TT3/TT4, and high T3 uptake, which aligns with the described description for this condition. If TSH were high, that would point away from primary hyperthyroidism and toward a pituitary or other secondary problem.