What treatment should be delayed until 1 hour after administering Propylthiouracil (PTU) or Methimazole in a patient with thyroid storm?

C. Potassium Iodide

Potassium iodide (or other iodine solutions) must be delayed until 1-2 hours after administering PTU or methimazole in thyroid storm treatment. 1

Critical Timing Rationale

The sequencing of medications in thyroid storm is essential because:

• Iodine administered before thionamides can paradoxically worsen thyrotoxicosis by providing substrate for new thyroid hormone synthesis 1, 2
• Thionamides (PTU or methimazole) must be given first to block thyroid hormone synthesis before iodine is introduced 1
• Once thionamides are on board, iodine can then safely block thyroid hormone release from the gland 1

Standard Treatment Algorithm for Thyroid Storm

Step 1: Block Thyroid Hormone Synthesis (Immediate)

• Propylthiouracil is preferred as first-line because it inhibits both thyroid hormone synthesis AND peripheral conversion of T4 to T3 1
• Methimazole is an acceptable alternative if PTU is unavailable 1

Step 2: Block Thyroid Hormone Release (1-2 Hours Later)

• Administer saturated potassium iodide solution or sodium iodide 1-2 hours after starting thionamides 1, 2
• This timing is non-negotiable to prevent worsening thyrotoxicosis 1

Step 3: Control Adrenergic Effects (Can Be Given Concurrently)

• Beta-blockers (propranolol 60-80 mg orally every 4-6 hours) are essential for controlling tachycardia and cardiovascular symptoms 3, 1
• Propranolol has the added benefit of blocking peripheral T4 to T3 conversion 1
• In hemodynamically unstable patients, esmolol is preferred due to its ultra-short half-life 1

Step 4: Reduce Peripheral Conversion (Can Be Given Concurrently)

• Corticosteroids (dexamethasone or hydrocortisone) reduce peripheral T4 to T3 conversion and treat potential relative adrenal insufficiency 1, 2
• These can be administered immediately without timing restrictions 1

Why Other Options Are Incorrect

• Antibiotics (A): No timing restriction exists; these should be given immediately if infection is the precipitating cause 3
• Hydrocortisone (B): Can be administered immediately as part of initial management 1, 2
• Propranolol (D): Should be started immediately to control life-threatening cardiovascular symptoms 3, 1

Common Pitfall

The most dangerous error in thyroid storm management is administering iodine before thionamides, which can dramatically worsen the patient's condition by providing substrate for accelerated thyroid hormone synthesis 1, 2. Always ensure thionamides have been given at least 1 hour prior to iodine administration.