Elevated TSH with low thyroid hormone indicates dysfunction of which gland?

Elevated TSH with low thyroid hormone indicates dysfunction of which gland?

• A. Pituitary gland
• B. Hypothalamus
• C. Adrenal gland
• D. Thyroid gland

Answer: (D)

The thyroid gland. In the hypothalamic–pituitary–thyroid axis, the hypothalamus releases TRH to stimulate the pituitary to make TSH, which then tells the thyroid to produce T4 and T3. When thyroid hormone levels are low, the pituitary raises TSH in an attempt to boost thyroid output. If the thyroid itself cannot respond adequately, TSH remains elevated while thyroid hormone stays low, indicating a primary thyroid gland problem. If the issue were in the pituitary or hypothalamus, TSH would be low or inappropriately normal despite low thyroid hormone. The adrenal gland is not part of this thyroid feedback loop.

The thyroid gland. In the hypothalamic–pituitary–thyroid axis, the hypothalamus releases TRH to stimulate the pituitary to make TSH, which then tells the thyroid to produce T4 and T3. When thyroid hormone levels are low, the pituitary raises TSH in an attempt to boost thyroid output. If the thyroid itself cannot respond adequately, TSH remains elevated while thyroid hormone stays low, indicating a primary thyroid gland problem. If the issue were in the pituitary or hypothalamus, TSH would be low or inappropriately normal despite low thyroid hormone. The adrenal gland is not part of this thyroid feedback loop.