A patient exhibits elevated TSH despite normal T3 and T4 levels, but the thyroid gland appears structurally normal via ultrasound. What explains this phenomenon?

💡 Explanation

TSH elevation with normal T3/T4 indicates the pituitary is over-secreting TSH, because the thyroid is functioning properly. A TSH-secreting adenoma would cause this, therefore the pituitary is the problem, rather than the thyroid itself or peripheral resistance.

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