Should a 51‑year‑old euthyroid woman with negative thyroid antibodies who is taking natural desiccated thyroid (NP Thyroid) and prednisolone acetate 1% eye drops for thyroid eye disease discontinue her iodine‑potassium iodide supplement?

Discontinue Iodine-Potassium Iodide Supplement Immediately

This 51-year-old euthyroid woman with negative thyroid antibodies who is already on thyroid hormone replacement (NP Thyroid) should discontinue her iodine-potassium iodide supplement, as there is no indication for supplemental iodine in a patient already receiving adequate thyroid hormone therapy, and excess iodine can trigger thyroid dysfunction. 1

Rationale for Discontinuation

Current Thyroid Status

• Her TSH is 2.11 mIU/L with T4 0.94 ng/dL and T3 2.3 pg/mL, indicating she is biochemically euthyroid on her current NP Thyroid 60 mg daily dose 2
• Thyroid peroxidase antibodies (6) and thyroglobulin antibodies (<1) are negative, ruling out autoimmune thyroid disease as the underlying etiology 2
• Euthyroid patients on adequate thyroid hormone replacement do not require iodine supplementation, as the thyroid gland is already being bypassed by exogenous hormone therapy 1

Risks of Excess Iodine in This Patient

Iodine-potassium iodide supplements deliver pharmacologic doses of iodine that far exceed physiologic needs (150-300 mcg/day) and can cause significant harm: 1

• Iodine-induced thyroid dysfunction (Jod-Basedow phenomenon): Excess iodine can trigger hyperthyroidism, particularly in patients with autonomous thyroid nodules or underlying thyroid pathology 3
• Interference with thyroid hormone regulation: Large iodine loads can disrupt the hypothalamic-pituitary-thyroid axis even in patients on replacement therapy 1
• Potential worsening of thyroid eye disease: While this patient is being treated with prednisolone acetate 1% eye drops for presumed thyroid eye disease, maintaining stable euthyroid status is critical, and excess iodine could destabilize thyroid function 4

No Benefit in This Clinical Context

• Adequate iodine intake (150 mcg/day) is already achieved through normal dietary sources including iodized salt, and the WHO recommends universal salt iodization as the primary strategy for iodine sufficiency 1
• Patients on thyroid hormone replacement do not require their thyroid gland to produce hormone, making iodine supplementation physiologically unnecessary 1
• Routine iodine restriction is not indicated in euthyroid patients, but pharmacologic iodine supplementation is equally inappropriate without specific medical indication 3

Management of Thyroid Eye Disease Considerations

The prednisolone acetate 1% eye drops suggest active thyroid eye disease management: 5, 4

• Maintaining stable euthyroid status is paramount in thyroid eye disease, as both hypo- and hyperthyroidism can worsen orbital inflammation 4
• Excess iodine poses a risk of inducing thyroid dysfunction that could exacerbate thyroid eye disease activity 4
• Continue the NP Thyroid 60 mg daily to maintain current euthyroid state, with TSH monitoring every 6-12 weeks initially 2

Monitoring Plan After Iodine Discontinuation

Repeat thyroid function tests (TSH, free T4, T3) in 6-8 weeks after discontinuing iodine supplement: 2

• If TSH remains between 0.5-4.5 mIU/L with normal free T4, continue current NP Thyroid dose 2
• If TSH drifts above 4.5 mIU/L, consider small dose adjustment of NP Thyroid (increase by 15-30 mg daily) 2
• Monitor for symptoms of thyroid dysfunction including fatigue, weight changes, palpitations, or worsening eye symptoms 5

Common Pitfalls to Avoid

• Do not continue iodine supplementation based on misconceptions about "thyroid support" – patients on thyroid hormone replacement do not benefit from additional iodine 1
• Avoid non-dietary iodine sources including iodinated contrast agents when possible, topical povidone-iodine, and amiodarone, as these deliver massive iodine loads 1
• Do not assume iodine is benign – pharmacologic iodine supplementation carries real risks of inducing thyroid dysfunction in susceptible individuals 3