A patient with a TSH-secreting pituitary adenoma (thyrotropinoma) has elevated TSH, elevated free T4, and elevated free T3. This differs from Graves' disease in that:

• A Graves' disease shows elevated TSH; thyrotropinoma shows suppressed TSH
• B Thyrotropinoma causes T4 elevation without T3 elevation; Graves' disease raises both
• C In thyrotropinoma, TSH is inappropriately elevated (not suppressed) despite elevated thyroid hormones, indicating loss of negative feedback at the pituitary level; in Graves', elevated T4/T3 appropriately suppresses TSH to undetectable levels ✓
• D Thyrotropinoma is associated with anti-TSH receptor antibodies; Graves' disease is not

Explanation

The key distinguishing feature is the TSH level relative to thyroid hormone levels. In Graves' disease (primary hyperthyroidism), elevated T3/T4 normally suppresses pituitary TSH secretion to undetectable levels via negative feedback — TSH is <0.01 mIU/L. In a thyrotropinoma (secondary/central hyperthyroidism), the adenoma secretes TSH autonomously, inappropriately high despite elevated T4/T3 — TSH is normal or elevated (typically 2-10 mIU/L). This 'inappropriate TSH' pattern (elevated TSH with elevated FT4/FT3) is diagnostic of thyrotropinoma. Graves' disease is due to TSH receptor-stimulating antibodies (TRAb), while thyrotropinoma has no TRAb.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

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Written and medically reviewed by the StethoPrep medical team.