In thyroid storm, which medication is used to inhibit thyroid hormone synthesis and peripheral conversion?

In thyroid storm, which medication is used to inhibit thyroid hormone synthesis and peripheral conversion?

• A. Oxygen
• B. Propranolol
• C. PTU
• D. Cooling

Answer: (C)

In thyroid storm, you aim to rapidly lower thyroid hormone levels by both stopping new hormone production and reducing the active hormone in circulation. Propylthiouracil is best because it does two things: it inhibits thyroid peroxidase, blocking synthesis of new thyroid hormones, and it also inhibits 5'-deiodinase, which reduces the conversion of T4 to the more active T3 in peripheral tissues. That dual action addresses both production and peripheral activation. Propranolol helps by blunting sympathetic symptoms and may modestly reduce peripheral conversion at high doses, but it does not inhibit hormone synthesis. Oxygen and cooling are supportive but do not affect how much hormone is produced or converted.

In thyroid storm, you aim to rapidly lower thyroid hormone levels by both stopping new hormone production and reducing the active hormone in circulation. Propylthiouracil is best because it does two things: it inhibits thyroid peroxidase, blocking synthesis of new thyroid hormones, and it also inhibits 5'-deiodinase, which reduces the conversion of T4 to the more active T3 in peripheral tissues. That dual action addresses both production and peripheral activation.

Propranolol helps by blunting sympathetic symptoms and may modestly reduce peripheral conversion at high doses, but it does not inhibit hormone synthesis. Oxygen and cooling are supportive but do not affect how much hormone is produced or converted.