Question

A patient has fatigue but is not gaining weight, and the body feels warm. Investigations are most likely to show:

• A. Low TSH with raised T3 or T4
• B. High TSH with normal T3 or T4
• C. High TSH with a euthyroid state
• D. Increased uptake of T3 but decreased T4

Hint:

A warm patient who will not gain weight is running hot; think about what the pituitary does when thyroid hormone is high.

Answer 1

The Correct Option is A

Translate the symptoms first. Warm skin plus an inability to put on weight equals a body burning energy too fast, the textbook hypermetabolic syndrome of thyrotoxicosis. Now reason from negative feedback, the core principle of the thyroid axis. When the thyroid gland pumps out excess T3 and T4, those hormones feed back onto the anterior pituitary and shut down TSH secretion. So the lab signature of primary hyperthyroidism is the mirror image: thyroid hormones up, TSH down. Scan the options with that rule. Any choice that starts with high TSH belongs to hypothyroidism, where the patient would feel cold and gain weight, so options B and C are out. The decreased T4 with increased T3 uptake option does not fit a hyperthyroid clinical state either. The only internally consistent answer is a suppressed TSH with elevated T3 or T4.