Hyperthyroidism is characterized by which hormonal change?

Hyperthyroidism is characterized by which hormonal change?

• A. Decreased T3 and T4
• B. Normal T3 and T4
• C. Increased T3 and T4
• D. Increased TRH only

Answer: (C)

Hyperthyroidism is defined by an excess of thyroid hormones in the body, so the key hormonal change is increased levels of T3 and T4 in the bloodstream. This surplus speeds up the body's metabolism, producing symptoms like weight loss, heat intolerance, fast heart rate, anxiety, and tremors. The elevated T3 and T4 also suppress the pituitary and hypothalamus via negative feedback, so TSH (and TRH) levels typically fall. The other patterns don’t fit: decreased T3/T4 points to hypothyroidism, normal levels indicate euthyroid status, and increased TRH alone would not sustain hyperthyroidism since the system would normally reduce TRH and TSH when T3/T4 are high.

Hyperthyroidism is defined by an excess of thyroid hormones in the body, so the key hormonal change is increased levels of T3 and T4 in the bloodstream. This surplus speeds up the body's metabolism, producing symptoms like weight loss, heat intolerance, fast heart rate, anxiety, and tremors. The elevated T3 and T4 also suppress the pituitary and hypothalamus via negative feedback, so TSH (and TRH) levels typically fall. The other patterns don’t fit: decreased T3/T4 points to hypothyroidism, normal levels indicate euthyroid status, and increased TRH alone would not sustain hyperthyroidism since the system would normally reduce TRH and TSH when T3/T4 are high.