Physiology The enzyme primarily responsible for the conversion of T4 to T3 in the periphery is A D1 thyroid deiodinase B D2 thyroid deiodinase C D3 thyroid deiodinase D Thyroid peroxidase 💡 Explanation The enzyme primarily responsible for the conversion of T4 to T3 in the periphery is ✓ Correct Answer: A. D1 thyroid deiodinase