TSH 0.3 mIU/L with Free T4 1.9 ng/dL indicates?

TSH 0.3 mIU/L with Free T4 1.9 ng/dL indicates?

• A. Hyperthyroidism
• B. Hypothyroidism
• C. Euthyroid
• D. Subclinical hypothyroidism

Answer: (D)

Low TSH with a normal-to-high Free T4 points to hyperthyroid activity, even if the Free T4 isn’t clearly elevated. Here, the TSH is suppressed at 0.3 mIU/L, and the Free T4 is 1.9 ng/dL, which is at the upper end of normal or mildly elevated depending on the assay. When TSH is suppressed but Free T4 remains normal, this pattern is called subclinical hyperthyroidism. If Free T4 were definitively elevated, it would be overt hyperthyroidism. Subclinical hypothyroidism, by contrast, shows a high TSH with a normal Free T4, which is not the case here.

Low TSH with a normal-to-high Free T4 points to hyperthyroid activity, even if the Free T4 isn’t clearly elevated. Here, the TSH is suppressed at 0.3 mIU/L, and the Free T4 is 1.9 ng/dL, which is at the upper end of normal or mildly elevated depending on the assay. When TSH is suppressed but Free T4 remains normal, this pattern is called subclinical hyperthyroidism. If Free T4 were definitively elevated, it would be overt hyperthyroidism. Subclinical hypothyroidism, by contrast, shows a high TSH with a normal Free T4, which is not the case here.