A patient presents with anxiety, weight loss, hyperactivity and insomnia. Routine tests diagnose hyperthyroidism. Which thyroid function test pattern is most likely?

A patient presents with anxiety, weight loss, hyperactivity and insomnia. Routine tests diagnose hyperthyroidism. Which thyroid function test pattern is most likely?

• A. High TSH and high FT4
• B. Low TSH and low FT4
• C. Normal TSH and FT4
• D. Low TSH and high FT4

Answer: (D)

When the thyroid is overactive, it pumps out more hormone, and that excess circulating hormone feeds back to the pituitary to shut down TSH production. The result is high free T4 (and often high free T3) with a suppressed TSH. The symptoms described (anxiety, weight loss, hyperactivity, insomnia) fit hyperthyroidism, so the expected lab pattern is a low TSH with a high FT4.

When the thyroid is overactive, it pumps out more hormone, and that excess circulating hormone feeds back to the pituitary to shut down TSH production. The result is high free T4 (and often high free T3) with a suppressed TSH. The symptoms described (anxiety, weight loss, hyperactivity, insomnia) fit hyperthyroidism, so the expected lab pattern is a low TSH with a high FT4.