Which statement best describes subclinical hypothyroidism?

Which statement best describes subclinical hypothyroidism?

• A. TSH is elevated with normal Free T4.
• B. TSH is elevated with low Free T4.
• C. TSH is normal with high Free T4.
• D. TSH is elevated with high Free T4.

Answer: (A)

Subclinical hypothyroidism is characterized by an elevated TSH with a normal Free T4. The pituitary gland increases TSH to stimulate the thyroid because tissue-level thyroid hormone activity is perceived as low, but the circulating Free T4 remains within the normal reference range. This distinguishes it from overt hypothyroidism, where Free T4 would be low, and from hyperthyroid states, where TSH would be suppressed or Free T4 would be high. So, the pattern of high TSH with normal Free T4 best describes subclinical hypothyroidism.

Subclinical hypothyroidism is characterized by an elevated TSH with a normal Free T4. The pituitary gland increases TSH to stimulate the thyroid because tissue-level thyroid hormone activity is perceived as low, but the circulating Free T4 remains within the normal reference range. This distinguishes it from overt hypothyroidism, where Free T4 would be low, and from hyperthyroid states, where TSH would be suppressed or Free T4 would be high. So, the pattern of high TSH with normal Free T4 best describes subclinical hypothyroidism.