Which gland is evaluated by measuring blood levels of T3 and T4?

Which gland is evaluated by measuring blood levels of T3 and T4?

• A. Thyroid gland
• B. Pancreas
• C. Pituitary gland
• D. Thymus

Answer: (A)

Measuring T3 and T4 in the blood directly assesses the thyroid gland’s activity. These hormones are produced by the thyroid and set the body’s metabolic rate, influencing temperature regulation, heart rate, energy use, and growth. When thyroid output is high, metabolism speeds up; when it’s low, metabolism slows down. The pituitary participates by releasing TSH in response to circulating hormone levels, creating a feedback loop, but the tissue that actually makes T3 and T4 is the thyroid gland. The other glands listed don’t produce these hormones—the pancreas makes insulin and glucagon, the thymus is involved in immune development, and the pituitary releases hormones that regulate other glands.

Measuring T3 and T4 in the blood directly assesses the thyroid gland’s activity. These hormones are produced by the thyroid and set the body’s metabolic rate, influencing temperature regulation, heart rate, energy use, and growth. When thyroid output is high, metabolism speeds up; when it’s low, metabolism slows down. The pituitary participates by releasing TSH in response to circulating hormone levels, creating a feedback loop, but the tissue that actually makes T3 and T4 is the thyroid gland. The other glands listed don’t produce these hormones—the pancreas makes insulin and glucagon, the thymus is involved in immune development, and the pituitary releases hormones that regulate other glands.