Which set of substances is used to assess thyroid function by hormone levels?

Which set of substances is used to assess thyroid function by hormone levels?

• A. ACTH and TSH
• B. Calcium and phosphorus
• C. Sodium and potassium
• D. T3 and T4

Answer: (D)

Thyroid function is determined by the hormones the gland actually produces. The two primary thyroid hormones are T4 (thyroxine) and T3 (triiodothyronine). Measuring their levels in the blood, often the free fractions, provides a direct readout of thyroid output and helps identify whether the gland is under- or overactive. While other hormones like ACTH or TSH relate to regulation of the thyroid system, they are not the thyroid hormones themselves, and calcium/phosphorus or sodium/potassium values relate to different physiological processes. So, the substances used to assess thyroid function by hormone levels are T3 and T4.

Thyroid function is determined by the hormones the gland actually produces. The two primary thyroid hormones are T4 (thyroxine) and T3 (triiodothyronine). Measuring their levels in the blood, often the free fractions, provides a direct readout of thyroid output and helps identify whether the gland is under- or overactive. While other hormones like ACTH or TSH relate to regulation of the thyroid system, they are not the thyroid hormones themselves, and calcium/phosphorus or sodium/potassium values relate to different physiological processes. So, the substances used to assess thyroid function by hormone levels are T3 and T4.