Iodine (I₂ / I⁻)
I₂ forms 6-IL (PPARγ agonist) for mito apoptosis (caspase/Bax), ↓ VEGF/angio, estrogen shift, variable NIS; thyroid ⚠ (TSH/T4 ↕). Small breast RCT: 5 mg/day + chemo ↑ pCR/↓ AEs; monitor thyroid—adjunct in ER+ breast, avoid peri-RAI.
Forms: Oral Lugol's solution (Rx/supplement, 5–12.5 mg I₂) · Potassium iodide tablets (OTC, 150 mcg)
Key Takeaway
Best studied as molecular iodine (I₂) with standard therapy—especially in breast cancer—where it may trigger PPARγ-driven apoptosis, temper angiogenesis, and improve chemo response in a small RCT. Because iodine strongly affects the thyroid and radioiodine treatments, use only with clinician oversight and avoid around planned I-131 therapy.
Evidence at a glance
Moderate clinical (small RCT + biomarkers) + strong preclinical; breast-focused, thyroid rules apply.
How it may work
Outside thyroid cancer care, I₂ can be converted to 6-iodolactone (6-IL), a PPARγ ligand that promotes mitochondrial apoptosis (Bax↑/Bcl-2↓, cytochrome-c release, caspase-3/7). Iodine can downshift VEGF/HIF-1α programs and modulate estrogen biology. A randomized, double-blind trial adding 5 mg/day I₂ to neoadjuvant chemo in breast cancer reported higher pCR rates and fewer AEs. High iodine competes with radioiodine uptake; avoid before I-123/I-131 imaging/therapy.
Targets & pathways
Curated mechanistic targets reported for this agent — how it may act on cells, not proof of a clinical effect.
- PPARγ↑Via 6-iodolactone; promotes apoptosis
- Apoptosis↑Mitochondrial (Bax↑/Bcl-2↓, caspase-3/7)
- VEGF/HIF-1α↓Inhibits angiogenesis
- Estrogen Modulation↕Shifts metabolism; ER-α effects
- NIS↕Variable iodide uptake in tumors
- Thyroid Axis↕TSH/T4/T3 modulation; Wolff-Chaikoff risk
Often studied / combined with
Combinations reported in the literature, not a protocol or a recommendation.
- Neoadjuvant chemo (e.g., anthracycline/taxane): pCR ↑, AEs ↓ in breast RCT.
Overlapping mechanisms
- PPARγ ↑ / Apoptosis ↑ / Angio ↓: Avoid with other PPARγ/apoptotics/anti-angio; thyroid risk compounds.
Safety & interactions
Severity and how well-established each signal is are shown separately. Verify everything with your oncologist or pharmacist — absence here does not mean safe.
- Amiodarone / LithiumAvoidSevereTheoreticalExacerbates thyroid toxicity.
- Iodinated contrast / AntisepticsMonitorModerateTheoreticalCumulative iodine load.
- Neoadjuvant chemo (breast)ConsiderBeneficialTheoreticalpCR ↑, AEs ↓ per RCT.
Timing
- With meals: Reduces GI upset.
- Daily continuous: 5 mg I₂ for adjunct protocols.
- Pre-chemo baseline: Thyroid function check before starting.
References
- Nutrients 2019 — I₂ (5 mg/day) + neoadjuvant chemo improved pCR & reduced AEs (breast cancer RCT).
- Endocr Relat Cancer 2008 — 6-iodolactone activates PPARγ → apoptosis in breast cancer cells.
- Arch Med Sci 2022 — Variable NIS expression in human breast tumors.
- ATA — Low-iodine diet guidance before radioiodine.
Research
No published studies for Iodine (I₂ / I⁻) yet
New studies appear here once they’ve been reviewed. Browse all studies.
Dose: as studied, not a recommendation
Ranges seen in adjunct / practice use: 5–12.5 mg (po) Breast adjunct RCT: 5 mg I₂/day with chemo. General: 150 mcg–1 mg/day maintenance; up to 12.5 mg/day short-term. Preclinical HED from rat (0.05–0.2 mg/kg) ~0.008–0.032 mg/kg (~0.56–2.24 mg for 70 kg); human trials higher for oncology., As I₂ (Lugol's); not KI for non-thyroid use. Titrate; urinary iodine test baseline. Cycle if long-term; MD oversight essential for thyroid/RAI..
Trials studying Iodine (I₂ / I⁻)
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