In terms of thyroid hormone potency, which hormone is the most potent?

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Multiple Choice

In terms of thyroid hormone potency, which hormone is the most potent?

Potency of thyroid hormones is tied to how strongly they activate the thyroid hormone receptor and drive gene transcription. The active form, triiodothyronine, binds the receptor with higher affinity and has greater intrinsic activity than thyroxine, so per molecule it produces a stronger metabolic response. Thyroxine, produced in larger amounts, serves as a circulating reservoir and is converted in tissues to T3, which is why it’s less potent on a per-molecule basis despite its abundance. Calcitonin, while important for calcium homeostasis, acts through a different receptor and isn’t in the same thyroid hormone potency context as T3 and T4. Therefore, the most potent hormone among the options is triiodothyronine.

Potency of thyroid hormones is tied to how strongly they activate the thyroid hormone receptor and drive gene transcription. The active form, triiodothyronine, binds the receptor with higher affinity and has greater intrinsic activity than thyroxine, so per molecule it produces a stronger metabolic response. Thyroxine, produced in larger amounts, serves as a circulating reservoir and is converted in tissues to T3, which is why it’s less potent on a per-molecule basis despite its abundance. Calcitonin, while important for calcium homeostasis, acts through a different receptor and isn’t in the same thyroid hormone potency context as T3 and T4. Therefore, the most potent hormone among the options is triiodothyronine.

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