Myo-Inositol and Hashimoto's: A Promising but Small Evidence Base

Myo-inositol, especially when combined with selenium, has shown promising results in small clinical trials — lowering TSH and TPO antibodies in people with Hashimoto's and subclinical hypothyroidism. The evidence is still limited by small sample sizes and mostly one research group, but the biological mechanism is well established and the safety profile is good.

Why myo-inositol matters for thyroid health

Myo-inositol is a naturally occurring sugar alcohol found in many foods — particularly cantaloupe, citrus fruits, beans, and whole grains. Your body also synthesizes it. For decades it was mainly studied in the context of polycystic ovary syndrome (PCOS), but a body of research has now established a specific and important role in thyroid physiology.

Here's the mechanism: thyroid-stimulating hormone (TSH) released by the pituitary gland works by binding to receptors on thyroid cells and triggering a chain of intracellular signals that lead to thyroid hormone production. Two distinct signaling pathways are involved — one driven by cyclic AMP (cAMP), and one driven by the phosphoinositide (PI) pathway. Myo-inositol is the precursor to phosphoinositides, making it a structural component of the second pathway [C4].

The PI pathway is the one responsible for generating hydrogen peroxide (H2O2), which is required for the iodination step in thyroid hormone synthesis. Without adequate myo-inositol feeding this pathway, that step can be impaired even when TSH is normal [C4]. Research by Benvenga, Nordio, and Unfer has described this as a kind of "functional myo-inositol deficit" — not a deficiency in the classical sense, but a relative insufficiency in the thyroid tissue that can contribute to subclinical hypothyroidism [C4].

The combination of myo-inositol with selenium makes sense from a mechanistic standpoint too: selenium supports the antioxidant enzyme glutathione peroxidase, which neutralizes the excess H2O2 that would otherwise cause oxidative damage in the thyroid. Together, the two nutrients may support thyroid hormone synthesis while limiting the oxidative stress that drives autoimmune inflammation.

What the research actually shows

The evidence for myo-inositol in Hashimoto's comes primarily from a series of randomized controlled trials conducted by Italian researchers — particularly the groups led by Nordio, Basciani, and Unfer.

A 2013 study by Nordio and Pajalich in the Journal of Thyroid Research tested combined myo-inositol (600 mg/day) plus selenium (83 mcg/day) against selenium alone in patients with subclinical hypothyroidism and Hashimoto's [C3]. After six months, the combination group showed significantly greater reductions in TSH, TPO antibodies, and thyroglobulin antibodies (TgAb) compared to selenium alone.

A 2017 study in the International Journal of Endocrinology by the same lead author enrolled 86 Hashimoto's patients with TSH between 3 and 6 µIU/mL [C1]. The myo-inositol plus selenium group saw TSH normalize and both TPO and TgAb levels fall significantly after six months. Participants also reported improvement in subjective wellbeing. The authors noted that some patients in the combination group avoided starting levothyroxine, though this was a secondary finding.

A second 2017 paper in the European Review for Medical and Pharmacological Sciences followed 168 patients in a larger replication attempt [C2]. Again, the combined myo-inositol plus selenium group outperformed selenium alone on TSH, TPO, and TgAb reductions at six months.

A 2021 comprehensive review by Benvenga, Nordio, Laganà, and Unfer synthesized the mechanism and clinical findings, concluding that the evidence supports myo-inositol as an underappreciated component of thyroid function and a potential therapeutic tool in subclinical hypothyroidism, particularly in the autoimmune setting [C4].

A 2024 network meta-analysis that compared multiple supplements for Hashimoto's found that the combination of selenium and myo-inositol was among the more favorable interventions for reducing TSH and antibody levels [C5].

Where the evidence is weaker

The limitations are real and worth naming directly. Nearly all the clinical trials in this space come from the same small group of Italian researchers. Independent replication from other institutions — a cornerstone of scientific confidence — is limited.

Sample sizes are small: the largest study had 168 participants, and most had fewer than 100. These trials were not blinded for myo-inositol taste or texture, which raises placebo effect concerns for subjective outcomes like wellbeing.

The studies enrolled patients with subclinical hypothyroidism — meaning TSH was mildly elevated but thyroid hormone levels were still technically normal. Whether myo-inositol plus selenium has the same effect in people with overt hypothyroidism already on levothyroxine is not well studied.

No study has followed participants beyond six months, so durability of any antibody reduction is unknown. And the question of whether reducing antibodies over six months translates to meaningful clinical outcomes (fewer symptoms, slower disease progression) hasn't been rigorously tested.

A 2025 comprehensive review acknowledged this evidence gap and called for larger, multi-center, long-duration trials before strong recommendations can be made [C6].

Practical guidelines

The studied doses are myo-inositol 600 mg/day combined with selenium 83 mcg/day. This is the combination used across the trials, and it's the dose to discuss with your healthcare provider if you're considering trying it [C1][C3]. Don't self-dose at higher levels without guidance.
This is a candidate intervention for subclinical hypothyroidism with Hashimoto's. If your TSH is mildly elevated (typically 3–6 µIU/mL) and you and your doctor are monitoring rather than treating, this is the population the studies focused on. It is not a substitute for levothyroxine when medication is clinically indicated.
Myo-inositol is widely available and has a good safety profile. It is generally well tolerated. Mild gastrointestinal symptoms (nausea, loose stools) have been reported at higher doses used in PCOS research. At the thyroid doses studied (600 mg/day), tolerability was good [C1][C2].
Get selenium from food first if possible. Brazil nuts are famously concentrated in selenium (one to two per day covers your needs). The myo-inositol + selenium RCTs supplemented selenium, but people with reasonable dietary selenium may need to be thoughtful about not over-supplementing selenium, which has a narrow therapeutic window.

Frequently asked questions

Can I take myo-inositol if I'm already on levothyroxine? The existing studies didn't systematically include patients already on levothyroxine, so the evidence is limited for that combination. There's no known interaction, but you should tell your doctor if you plan to add a supplement that may affect TSH — your dose might need re-evaluation.

Does myo-inositol alone work, without selenium? The studies used the combination. Some earlier mechanistic work suggests myo-inositol alone has effects on TSH signaling [C4], but the clinical trials that showed antibody reductions used both nutrients together. The selenium component is biologically plausible and the combination has the strongest evidence.

Is it the same myo-inositol used for PCOS? Yes — myo-inositol is the same molecule. PCOS studies typically use much higher doses (2,000–4,000 mg/day) focused on insulin signaling. The thyroid doses studied are much lower. If you're taking high-dose myo-inositol for PCOS, the thyroid findings likely don't extrapolate directly.

How long before I'd see any effect? The trials ran for six months. Any TSH or antibody changes in the studies became apparent within that window. Don't expect significant changes at two to four weeks.

Bottom line

Myo-inositol combined with selenium is one of the more biologically plausible nutrient interventions for Hashimoto's with subclinical hypothyroidism, supported by a handful of small Italian RCTs showing reductions in TSH and thyroid antibodies [C1][C2][C3]. The mechanism is well understood [C4], the safety profile is favorable, and the 2024 network meta-analysis places this combination among the better-supported supplement options [C5]. What's missing is independent replication from other research groups and longer follow-up data. It's a promising candidate worth discussing with your endocrinologist — not a proven treatment.

Sources

[C1] Nordio M, Basciani S. Treatment with Myo-Inositol and Selenium Ensures Euthyroidism in Patients with Autoimmune Thyroiditis. Int J Endocrinol. 2017;2017:2549491. PubMed: 28293260
[C2] Nordio M, Basciani S. Myo-inositol plus selenium supplementation restores euthyroid state in Hashimoto's patients with subclinical hypothyroidism. Eur Rev Med Pharmacol Sci. 2017;21(2 Suppl):51-59. PubMed: 28724185
[C3] Nordio M, Pajalich R. Combined treatment with Myo-inositol and selenium ensures euthyroidism in subclinical hypothyroidism patients with autoimmune thyroiditis. J Thyroid Res. 2013;2013:424163. PubMed: 24224112
[C4] Benvenga S, Nordio M, Laganà AS, Unfer V. The Role of Inositol in Thyroid Physiology and in Subclinical Hypothyroidism Management. Front Endocrinol. 2021;12:662582. PubMed: 34040582
[C5] Zhao Y, et al. Effects of different supplements on Hashimoto's thyroiditis: a systematic review and network meta-analysis. Front Endocrinol. 2024;15:1445878. frontiersin.org
[C6] Unlocking the Therapeutic Potential: Selenium and Myo-Inositol Supplementation in Thyroid Disorders — Efficacy and Future Directions. PubMed: 41157173

For educational purposes only. Not medical advice. Always consult your healthcare provider.