diiodotyrosine

HormoneThyroid hormone precursor

What is it

Diiodotyrosine (DIT) is an iodinated form of the amino acid tyrosine and is an intermediate in the synthesis of thyroid hormones T3 and T4. It is sometimes included in thyroid-support supplements.

Evidence for 1 use

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Thyroid hormone support

Mixed Evidence

DIT provides iodine, which is essential for thyroid hormone synthesis in people with adequate dietary iodine. There is no clear evidence that DIT offers benefits beyond what plain iodine and tyrosine provide.

How it works

Within the thyroid gland, iodide attaches to tyrosine residues on thyroglobulin to form monoiodotyrosine (MIT) and diiodotyrosine (DIT). Two DIT molecules couple to form T4; one MIT and one DIT form T3. Oral DIT delivers both iodine and tyrosine. The iodine content is biologically active and contributes to thyroid hormone synthesis just like iodine from any other source. There is no established physiological advantage to consuming DIT itself rather than potassium iodide and tyrosine separately.

Dosage

There is no established RDA for DIT itself. Iodine RDA is 150 mcg/day for adults (UL 1100 mcg/day). Tyrosine has no RDA. Products containing DIT typically list iodine content; total iodine from all sources should stay within the upper limit.

When and how to take it

If used, take consistently at the same time each day, separated from thyroid medication by at least 4 hours.

1 commercial form

Compare the main delivery options and what they’re best suited for.

3,5-Diiodo-L-tyrosine

Available in some specialty thyroid-support formulas.

Provides iodine and tyrosine on a per-molecule basis.

Safety

Excess iodine can trigger or worsen thyroid problems, including both hyperthyroidism and hypothyroidism. Even doses moderately above the RDA may cause issues in susceptible people. Tyrosine itself is well tolerated at typical supplement doses but can cause anxiety or insomnia in some users.

Who should be cautious

Avoid in pregnancy and breastfeeding unless prescribed; iodine needs increase but the margin between deficiency and excess is narrow. People with Hashimoto thyroiditis, Graves disease, or thyroid nodules should consult an endocrinologist before using DIT-containing products.

Interactions

Iodine-containing products interact with thyroid medications (levothyroxine, methimazole, propylthiouracil), amiodarone, lithium, and ACE inhibitors. People with autoimmune thyroid disease are especially sensitive to changes in iodine intake.

Food sources

Seaweed (iodine source)

Amount
Varies widely
%DV
—

Iodized salt (iodine source)

Amount
75 mcg per 1/4 tsp
%DV
50%

Frequently asked questions

Is diiodotyrosine the same as a thyroid hormone?⌄

No. DIT is an intermediate in thyroid hormone synthesis, not an active hormone. It does not directly raise T3 or T4.

Should I take diiodotyrosine for low energy?⌄

Self-treating suspected thyroid issues is not advised. Get thyroid labs first and discuss treatment options with a clinician.

References

diiodotyrosine on Wikidata — Wikidata link

diiodotyrosine (ChEBI:15768) — ChEBI link

diiodotyrosine (PubChem CID 9305) — PubChem link

diiodotyrosine on NIH DSLD (US supplement label database) — NIH Dietary Supplement Label Database link

Research on diiodotyrosine (PubMed search) — PubMed link

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Evidence-based·How we grade evidence

Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.