When thyroid hormone levels in the blood are high, the pituitary gland reduces production of thyroid-stimulating hormone. When thyroid-stimulating hormone levels are low, the thyroid gland produces thyroid hormones without normal regulatory control.
Evidence from Studies
Supporting (3)
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Normally, high thyroid hormone levels tell the brain to stop making TSH, but in these tumors, the brain can’t 'hear' that message because it’s missing the right receptors. This proves the feedback system works as claimed—when it breaks, things go wrong.
When there's too much thyroid hormone in the blood, the brain turns down the signal (TSH) that tells the thyroid to make more — this study shows that happening. Less TSH means the thyroid slows down, which is how the body keeps hormone levels balanced.
Fundamentally distinct roles of thyroid hormone receptor isoforms in a thyrotroph cell line are due to differential DNA binding.
When there’s too much thyroid hormone in the body, a specific protein in the pituitary gland (THRB) tells it to stop making TSH, which in turn tells the thyroid to slow down hormone production. This study proves that this shut-off switch works mainly through THRB.
Contradicting (1)
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Even when patients have high thyroid hormone levels, some still have high TSH—meaning their bodies aren’t responding properly to the usual 'turn off' signal. This breaks the rule the claim says always happens.
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