Introduction: 50 mg and 4 mg are two different drugs
Naltrexone is an opioid antagonist approved at 50 mg/day for treatment of opioid and alcohol dependence since 1984. In 1985, New York neurologist Bernard Bihari and pharmacologist Ian Zagon noted a paradox: doses 10–30 times lower produce the opposite clinical effect — not continuous blockade of μ-opioid receptors, but a short 4–6-hour blockade followed by a rebound increase in endogenous endorphins and met-enkephalin.
This is LDN — low-dose naltrexone, in the 1.5–4.5 mg/day range before sleep. The drug is the same; the effect is immunomodulatory, not antagonistic.
Over 40 years, more than 200 publications have accumulated, including RCTs in fibromyalgia, Crohn disease, multiple sclerosis, ME/CFS, dermatologic diseases, and chronic pain (Gouda 2026, PMID 42060160; Parkitny, PMID 24523339; McKenzie 2026, PMID 41893019).
The question of this article: where LDN in autoimmune Hashimoto thyroiditis is a justified option, and where it is a premature self-protocol.
🌀
Mechanism of Action of LDN
The key concept is the short duration of blockade. After 4.5 mg orally, peak plasma concentration is reached after 1 hour, with a half-life of 4 hours. By morning, the drug is absent from the blood, but the endogenous response continues.
▸Antagonism of μ- and δ-opioid receptors for 4–6 hours at night — the brain “thinks” endorphins are low and compensatorily initiates their synthesis. ▸Rebound increase ↑ β-endorphin, ↑ met-enkephalin for 12–24 hours after the drug disappears from plasma. ▸Blockade of TLR4 (Toll-like receptor 4) on microglia and macrophages — reduced neuroinflammation and lower IL-6, TNF-α production (Parkitny, PMID 24523339). ▸Th17 ↓ / Treg ↑ shift — remodeling of immune balance toward tolerance. ▸↓ IL-6, TNF-α, IL-17A — systemic reduction in pro-inflammatory cytokines. ▸Enhancement of the endogenous opioid system — analgesic and anxiolytic effects as a by-product.
Important: at doses >5 mg, LDN shifts into an antagonistic mode — blockade becomes prolonged, the rebound does not occur, and the immunomodulatory effect disappears. This explains why 50 mg in Hashimoto thyroiditis does not work, while 4.5 mg may.
🌀
Drivers of the Autoimmune Process in Hashimoto Thyroiditis
LDN does not treat the “cause” of Hashimoto thyroiditis — it remodels the immune response to thyroglobulin and thyroid peroxidase. To understand who may benefit, parallel triggers that should be corrected before or together with LDN must be listed.
•Selenium deficiency — via GPx and thioredoxin reductase, selenium suppresses oxidative stress in the thyrocyte and reduces TPO antibodies by 20–40% over 6 months at 200 mcg/day (Toulis 2010, PMID 20025778). •Vitamin D deficiency (<30 ng/mL) — a first-line immunomodulator; levels of 60–80 ng/mL are associated with lower AIT activity. •Visceral inflammation and insulin resistance — TNF-α from adipocytes sustains autoreactivity. •Increased intestinal permeability syndrome — zonulin-dependent leaky gut correlates with AIT activity; gluten is a trigger in some patients. •Chronic stress and cortisol — reduced Treg activity and Th17 activation. •EBV (Epstein–Barr virus) and reactivation — described as a trigger in a subset of patients. •High-dose iodine in selenium deficiency — paradoxical amplification of AIT.
The md_pereligyn protocol principle: correct the drivers first, then add LDN. Otherwise, LDN works “against the wind” and the effect is lower than expected.
🌀
Markers for Assessing Effect
Before starting LDN and every 3 months during therapy:
▸TPO antibodies (antibodies to thyroid peroxidase) — target decrease of 20–40% over 6 months. Reference <35 IU/mL; in AIT often 200–2000+. ▸Tg antibodies (antibodies to thyroglobulin) — a less dynamic marker, but useful for baseline phenotyping. ▸TSH (thyroid-stimulating hormone) — target 1.0–2.0 mIU/L on L-T4 replacement therapy. LDN itself does not change TSH. ▸fT4 (free thyroxine) — target upper half of the reference interval. ▸fT3 (free triiodothyronine) — 4.0–7.0 pmol/L; a marker of real tissue-level activity. ▸rT3 (reverse T3) — an indicator of “dead-end” conversion under stress and inflammation. ▸Vitamin D 25(OH)D — target 60–80 ng/mL. ▸Serum selenium — target 120–150 mcg/L. ▸Ferritin — ≥70 ng/mL (cofactor for thyroid hormone synthesis). ▸hsCRP — marker of systemic inflammation, target <1 mg/L.
Without this monitoring, LDN becomes a slot machine. With it, LDN becomes a controlled intervention.
🌀
Holistic Protocol: LDN in Context
LDN is third line, not first line. Sequence of use:
### 1. Baseline Replacement Therapy
▸Levothyroxine (L-T4) at a dose that maintains TSH 1.0–2.0 mIU/L and fT4 in the upper half of the reference range. With pronounced symptoms of low fT3, discuss T4 + T3 combination therapy or NDT (see the article [Hypothyroidism and natural desiccated thyroid (NDT)](/blog/hypothyroidism-natural-desiccated-thyroid-ndt)). ▸Recheck 6–8 weeks after any dose change.
### 2. Cofactors and Correction of Deficiencies
▸Selenium (L-selenomethionine) 200 mcg/day in the morning on an empty stomach, for at least 6 months. The core evidence-based foundation in AIT. ▸Vitamin D3 4000–10000 IU until 60–80 ng/mL, + K2 (MK-7) 100–200 mcg for calcium homeostasis safety. ▸Zinc 15–25 mg as bisglycinate or picolinate. ▸Magnesium (glycinate / taurate) 300–400 mg in the evening — cofactor for T4 → T3 conversion. ▸Iron when ferritin is <70 ng/mL — bisglycinate 25 mg every other day with vitamin C.
### 3. Gut and Nutrition
▸Mediterranean / DASH pattern, elimination of ultra-processed food. ▸Gluten-free diet — discuss in confirmed celiac disease or anti-tTG-IgA positivity; in some patients with seronegative sensitivity, it reduces TPO antibodies. ▸Probiotics (Lactobacillus, Bifidobacterium) in confirmed dysbiosis. ▸Butyrate and L-glutamine for leaky gut — for 8–12 weeks.
### 4. LDN — Point of Initiation
▸Start 1.5 mg in the evening (21:00–22:00), for 4 weeks. ▸+1.5 mg every 4–6 weeks if well tolerated. ▸Target dose 3.0–4.5 mg/day; in rare cases, 4.5 mg is the ceiling. ▸The preparation is compounded — the standard 50 mg formulation does not provide the required doses. In the Russian Federation, a compounded form is unavailable; in UA / PL / US / UK, it is available in specialized pharmacies. ▸Effect in 6–12 weeks, with assessment of TPO antibodies and symptoms at months 3 and 6. ▸Course duration — 12–18 months, followed by an attempt at gradual discontinuation if target markers are reached.
Principle: if there is no biochemical or symptomatic response after 6 months on 4.5 mg + corrected drivers, discontinue LDN and look for other causes of residual AIT activity.
🌀
Where the Evidence Base Exists (Beyond the Thyroid)
There are no direct RCTs in AIT — this must be stated immediately. However, the mechanistic basis and small-transfer effect from other autoimmune models make LDN a rational option.
▸Fibromyalgia — several RCTs and cohort studies (Moser 2025, PMID 40491623; Aalto 2025, PMID 41399763). ▸Chronic pain — a modern mechanistic review (McKenzie 2026, PMID 41893019). ▸Crohn disease, rheumatoid arthritis — review of clinical use (de Carvalho 2023, PMID 37223594). ▸ME/CFS — TRPM3 channel modulation as one proposed mechanism (Löhn 2024, PMID 38970055). ▸Dermatologic diseases — psoriasis, lichen planus, atopic dermatitis (Zhou 2026, PMID 40962192). ▸Autoimmune thyroiditis — case series and observational data. Snapshot effect on TPO antibodies in real-world patients with Hashimoto thyroiditis.
🌀
Who Should Consider LDN for the Thyroid
▸Persistent TPO antibodies >500 IU/mL despite adequate replacement therapy and corrected selenium / vitamin D / ferritin deficiencies. ▸Residual symptoms (fatigue, brain fog, diffuse myalgias) with normal TSH and fT4 — discuss with a physician after excluding other causes. ▸Overlap syndromes — Hashimoto thyroiditis + fibromyalgia / IBS / Crohn disease / RA / MS / vitiligo. Here LDN may work on both fronts. ▸Resistant chronic pain combined with AIT. ▸Progressive decline in thyroid function with rising TPO antibodies despite a complete nutraceutical protocol.
🌀
What Does NOT Work (and Why)
▸LDN as monotherapy for overt hypothyroidism — it does not replace L-T4. Thyrocytes that have already been destroyed are not restored by immunomodulation. Without replacement therapy, the patient decompensates. ▸LDN at 50 mg or 10 mg — this is no longer LDN; the effect is antagonistic, with no immunomodulation. ▸LDN without corrected selenium and vitamin D deficiencies — working “against the wind,” with a lower-than-expected effect and unjustified upward dose adjustment. ▸LDN with simultaneous use of any opioids (tramadol, codeine, tapentadol, oxycodone, methadone) — antagonism, withdrawal syndrome, absolute contraindication. ▸Self-prescribed LDN without TPO antibody and TSH monitoring — no feedback loop; effect cannot be assessed. ▸LDN during pregnancy and lactation — no data; not prescribed. ▸Rapid titration (+1.5 mg every week) — provokes vivid dreams, sleep disturbance, headaches. Standard titration is every 4–6 weeks.
🌀
Contraindications and Adverse Effects
Absolute contraindications:
▸Current use of any opioid analgesics (tramadol, codeine, tapentadol, oxycodone, morphine, fentanyl, methadone). ▸Acute liver failure. ▸Pregnancy and lactation (no data). ▸Decompensated depression with active suicidality.
Relative contraindications:
▸Active psoriasis flare (rare reports of provocation). ▸Severe chronic kidney disease, stages 4–5. ▸Concurrent use of HDL-dexamethasone or other strong immunosuppressants — discuss with the treating physician.
Adverse effects (usually transient, weeks 1–2):
▸Vivid dreams, difficulty falling asleep / maintaining sleep. ▸Morning muscle stiffness. ▸Transient GI symptoms (nausea, epigastric discomfort) at initiation. ▸Headache with rapid titration. ▸Less commonly — irritability, anxiety during the first days.
Most effects disappear by days 10–14. If they persist, reduce the dose by one step and reassess with a physician.
🌀
When to Seek Care
▸TPO antibodies >500 IU/mL persistently, despite a complete nutraceutical foundation and adequate L-T4 therapy for at least 6 months. ▸Symptoms (fatigue, brain fog, diffuse myalgias) with normal TSH and fT4 on standard therapy. ▸AIT overlap with another autoimmune condition (fibromyalgia, IBS, Crohn disease, RA, MS, vitiligo). ▸Progressive antibody increase despite deficiency correction. ▸Need for a personalized LDN plan with efficacy and safety monitoring.
I perform a complete status assessment (extended thyroid panel, selenium, vitamin D, ferritin, hsCRP, and when indicated anti-tTG-IgA and celiac disease evaluation), prepare an individualized protocol, and supervise LDN titration.
🌀
Conclusion
LDN is a rational third-line option in Hashimoto thyroiditis, not first-line therapy and not a self-protocol. It is a candidate when TPO antibodies remain persistently elevated despite adequate replacement therapy and corrected deficiencies. It does not replace L-T4, does not work properly without selenium and vitamin D, and is not used with opioids.
Dose 1.5–4.5 mg in the evening, stepwise titration, marker monitoring every 3 months, duration 12–18 months. Off-label use requires an informed patient choice and medical supervision.
Principle: drivers first, then the drug. LDN strengthens a competent protocol — it does not replace it.
🌀
Sources
▸Gouda NA. Low-dose naltrexone in chronic disease — comprehensive update. *Front Pharmacol* 2026. PMID 42060160 ▸Parkitny L, Younger J. Reduced pro-inflammatory cytokines after eight weeks of low-dose naltrexone for fibromyalgia. *Biomedicines* 2017;5:16. PMID 24523339 ▸McKenzie A, et al. Mechanisms of low-dose naltrexone in chronic pain. *Pain Res Manag* 2026. PMID 41893019 ▸de Carvalho J, et al. Low-dose naltrexone in autoimmune diseases — clinical review. *Autoimmun Rev* 2023;22. PMID 37223594 ▸Moser P, et al. Low-dose naltrexone in fibromyalgia: randomized trial. *Pain* 2025. PMID 40491623 ▸Aalto A, et al. Cohort study of LDN in fibromyalgia. *Eur J Pain* 2025. PMID 41399763 ▸Löhn M, et al. Low-dose naltrexone restores TRPM3 channel function in ME/CFS. *Front Immunol* 2024. PMID 38970055 ▸Zhou X, et al. Low-dose naltrexone in dermatology: psoriasis and lichen planus. *J Dermatol Treat* 2026. PMID 40962192 ▸Toulis KA, et al. Selenium supplementation in autoimmune thyroiditis. *Thyroid* 2010;20:1163–1173. PMID 20025778
Related articles: [Iodine and thyroid: 5 steps](/blog/iodine-thyroid-five-step-protocol), [Hypothyroidism and natural desiccated thyroid (NDT)](/blog/hypothyroidism-natural-desiccated-thyroid-ndt).
🌀
FAQ
Can LDN be started without confirmed Hashimoto thyroiditis? No. Before starting, there must be confirmation of TPO antibodies or Tg antibodies above the reference range and/or ultrasound features of AIT, as well as adequate replacement therapy for at least 6 months. LDN is an immunomodulator; its purpose is to manage an active autoimmune process, not to “try it just in case.”
How long until TPO antibodies decrease? Initial symptomatic shifts may appear after 6–8 weeks. Biochemical reduction in TPO antibodies usually takes 3–6 months. If there is no trend after 6 months on 4.5 mg with corrected deficiencies, LDN is discontinued and other causes are investigated (celiac disease, EBV reactivation, occult infection).
Can LDN be combined with levothyroxine? Yes, and this is the standard regimen. LDN does not affect L-T4 absorption or metabolism. They are taken at different times of day (L-T4 in the morning on an empty stomach, LDN in the evening before sleep).
What should be done about vivid dreams in the first week? This is an expected effect of the rebound increase in endorphins. It usually resolves by days 10–14. If dreams interfere with sleep, reduce the dose by one step or temporarily move administration to 18:00–19:00. Do not stop abruptly.
Can LDN be purchased in the Russian Federation? A compounded 1.5–4.5 mg form is unavailable in the Russian Federation. In UA, PL, EU, US, and UK, the drug is prepared in specialized compounding pharmacies by physician prescription. The key point: do not split 50 mg tablets yourself (the dose will be inaccurate and the effect unpredictable).
*This article is informational and does not replace medical consultation. Before starting any nutraceuticals, changing medication therapy, or undergoing diagnostic procedures, discuss the plan with your treating physician.*
