Tiratricol (TRIAC) – Kodiac biolabs

Our opinion on this compoundNiche research probe

41/100

A historical TR-beta probe now outclassed by resmetirom; retains niche value in RTH syndrome research

Look, TRIAC is one of those compounds that used to be the most interesting thing in its zip code and simply isn’t anymore. It’s a natural T3 metabolite, formed by deamination and oxidative decarboxylation of T3, and it retains thyroid receptor activity with a modest TR-beta preference somewhere around 2 to 4-fold over TR-alpha. That selectivity ratio was genuinely exciting in the 1980s and early 1990s when TR-beta-selective thyromimetics were a hot theoretical concept. It’s a lot less exciting now that resmetirom (Rezdiffra) has been FDA-approved for MASH with a vastly superior selectivity profile and a phase 3 dataset behind it.

The TR-beta biology here is real. TR-beta drives effects in the pituitary and liver; TR-alpha drives the cardiac and skeletal effects you don’t want. TRIAC’s selectivity is enough to produce the pituitary suppression you need in resistance to thyroid hormone syndrome (Refetoff syndrome) without the same degree of tachycardia and bone turnover you’d get from equivalent T3 exposure. That’s why it’s approved in France, Mexico, and a handful of other markets for RTH. It’s a legitimate approved compound with a real mechanism solving a real problem in a real patient population. We don’t want to dismiss that.

What we do want to flag is that the population is rare, the clinical trials were small, and the broader thyromimetic literature has moved decisively past TRIAC in terms of selectivity and precision. Sobetirome, VK2809, and now resmetirom all do the TR-beta job better. The fat loss angle, which drove a lot of the underground use, produced enough serious thyrotoxic events at supratherapeutic doses to prompt FDA enforcement actions against supplement products containing it. Thats not a research dead end exactly, but it is a credibility problem for any investigator trying to study TRIAC as a metabolic tool in 2025.

Where TRIAC still earns its place in a serious research library is as a reference thyromimetic. If you’re doing TR-beta selectivity work, you need a physiologically relevant natural metabolite as your comparator. TRIAC fills that role. It has decades of receptor-binding data, a well-characterized PK profile (roughly 7-hour half-life, shorter than T4, longer than T3), and the kind of historical dataset that lets you anchor new results against a known standard. The bench utility is real but bounded. You’re reaching for TRIAC when you need that physiological reference, not when you’re trying to advance the field.

Honestly, the score of 41 reflects exactly this situation: a compound that mattered, still has a defined niche, but isn’t where a serious investigator puts their next research dollar unless RTH syndrome or TR-beta reference biology is the specific program. Good tool. Not a frontier compound.

Novelty: 28
Mechanism promise: 45
In-category differentiation: 30
Evidence quality: 48
Translational signal: 50
Research bench value: 60

Rationale TRIAC scores low on novelty and differentiation because it’s a 1960s-era natural metabolite that has been materially superseded by far more selective thyromimetics; its bench value is the score’s floor, since it remains a physiologically relevant TR-beta reference compound and the only orally approved option for Refetoff syndrome in some jurisdictions.

T3 metabolite (3,3′,5-triiodothyroacetic acid)

A naturally occurring T3 metabolite with thyroid-receptor activity; used in resistance to thyroid hormone syndrome and (off-label) for fat loss.

Abstract

Tiratricol (TRIAC, 3,3′,5-triiodothyroacetic acid; CAS 51-24-1; molecular formula C14H9I3O4; molecular weight 621.93) is a natural T3 metabolite formed by deamination and oxidative decarboxylation of T3. The compound retains thyroid hormone receptor activity with TR-beta selectivity (approximately 2- to 4-fold over TR-alpha). Approved in France, Mexico, and other markets for resistance to thyroid hormone syndrome (Refetoff syndrome), where the TR-beta selectivity allows TR-beta target tissue (pituitary, liver) effects without the cardiac TR-alpha hyperthyroid effects. Off-label use in obesity and as an athletic fat-loss compound has been documented; the FDA has issued warnings against unapproved supplement products containing tiratricol owing to severe thyrotoxic adverse events at supratherapeutic doses. Plasma half-life is approximately 7 hours, shorter than T4 but longer than T3. Used as a reference TR-beta-selective thyromimetic in research.

Read the full monograph

The full reference document covers compound identification, discovery and developmental history, mechanism of action, pharmacokinetics, sourcing and quality verification, and a curated reference list. Embedded inline below; download for offline reading.

KDC-MN-291Open in new tab →

Download PDF →

FOR RESEARCH USE ONLY. Not for medical, diagnostic, or therapeutic purposes. Not for human consumption. All information is provided for research and educational purposes only.