Building a Ray Peat-Aligned Thyroid Stack: Research-Grade T3+T2, Cyproheptadine, and the Cleanest Profile

The bioenergetic research community has had decades to iterate on protocol design - and after years of single-compound experiments, dose-titration refinements, and systematic forum documentation of what works and what falls short, a consistent pattern has emerged. The thyroid stack that the community converges on is not a single compound. It is a three-component combination: sustained-release T3 (SR-T3) as the nuclear receptor keystone, 3,5-diiodothyronine (T2) as the direct mitochondrial activator, and cyproheptadine as the anti-serotonin lever. Each component targets a distinct node in the metabolic signal cascade. Each is necessary because the others leave a mechanism unaddressed.

This post walks through the Ray Peat-aligned thyroid stack from mechanism to sourcing. It explains what each component does, why the combination consistently outperforms single-compound protocols in the community's research discussion, and what sourcing standards matter when building a research-grade version of this stack. The sourcing section covers excipient profiles, purity verification, and the case for research-grade reference standards over the grey-market sourcing channels the community relied on in previous years.

The full framework context - the bioenergetic model's foundational position on T3, serotonin, and metabolic suppression - is developed in the Ray Peat protocol complete 2026 research guide. This post assumes familiarity with that framework and focuses specifically on the practical stack architecture.

Research framing. This post reviews the Ray Peat-aligned thyroid stack from a research-context standpoint. All compounds discussed are sold strictly for laboratory research and not for human consumption. See our FAQ legality page for full terms.

Why a Stack (Not a Single Compound)

Peat's framework positioned thyroid hormone as the metabolic keystone - the master regulator whose deficiency explains the overlapping presentations of chronic illness: low body temperature, fatigue, cognitive impairment, impaired oxidative phosphorylation, elevated reverse T3, and the whole clinical picture that mainstream endocrinology attributes to inadequate-TSH hypothyroidism while missing the T3-specific mechanism underneath it. That foundational framing is correct. What the protocol-iteration history of the research community reveals is that T3 alone, while necessary, is not sufficient.

The metabolic suppression that the bioenergetic framework targets is not a single-point failure. It is a multi-node dysfunction: impaired T4→T3 and T3→T2 deiodinase conversion at the conversion level; impaired mitochondrial Complex IV activation at the cellular energy level; and elevated serotonin acting as an active metabolic brake at the signaling level. A single-compound protocol targets one node while the others remain dysfunctional - which is the mechanistic explanation for the T3 plateau pattern the community documents consistently: serum T3 that appears adequate while metabolic markers stall.

The three-component stack targets all three nodes simultaneously. SR-T3 delivers the nuclear receptor-activating thyroid hormone directly, bypassing the T4→T3 conversion bottleneck. T2 activates the mitochondrial electron transport chain directly, bypassing the T3→T2 conversion bottleneck. Cyproheptadine blocks the 5-HT2A and 5-HT2C serotonin receptors, removing the serotonin-driven metabolic suppression that would otherwise blunt the response to both thyroid hormones. The three components are not redundant - they act on distinct mechanisms at distinct stages of the cascade. Single-compound protocols (T3 only, T2 only, cyproheptadine only) consistently underperform the combined stack in research-community discussion precisely because leaving two of those three nodes unaddressed means leaving two active sources of metabolic suppression in place.

Component 1: Sustained-Release T3 (SR-T3)

SR-T3 is the thyroid hormone keystone of the stack - the nuclear receptor activator that drives the genomic program of mitochondrial enzyme upregulation and metabolic rate elevation that T3's classical mechanism produces. The distinction between SR-T3 and immediate-release T3 (Cytomel, Cynomel, generic liothyronine) is not a marketing difference; it is a pharmacokinetic one that directly affects protocol tolerability and consistency.

Immediate-release T3 produces a sharp serum peak within 2-4 hours of dosing followed by a trough as the dose clears. That spike-and-trough profile - a 3-5x elevation in serum T3 above baseline within hours of dosing - is the source of the cardiovascular and adrenergic side effects that many researchers attribute to dose-titration error but that are, in significant part, intrinsic to the formulation. The rapid hormonal surge triggers an adrenergic response: palpitations, anxiety, the wired-then-tired pattern. SR-T3 solves this at the formulation level.

SR-T3 in a hydroxypropyl methylcellulose (HPMC) + microcrystalline cellulose (MCC) sustained-release matrix dissolves slowly as the capsule hydrates in the GI tract, releasing liothyronine over a 4-8 hour window rather than as an immediate bolus. The serum curve is fundamentally different: a lower, extended peak rather than a spike. The adrenergic effects associated with the serum spike are substantially attenuated because there is no spike. The trough-period fatigue is reduced because the decline is gradual. The receptor occupancy is more consistent across the dosing interval. These are pharmacokinetic advantages that no amount of immediate-release dose titration can replicate - the spike is built into the formulation, not correctable by reducing the dose.

The SR-T3 catalog covers five dose strengths: 7.5, 15, 22.5, 45, and 90 mcg. This five-point range is specifically designed to cover the full Wilson's WT3 titration ladder - from the initial low-dose entry at 7.5 mcg twice daily through the higher-dose phases of the titration cycle. All batches are HPLC-verified for potency and purity; the excipient profile is HPMC + MCC only. The full pharmacokinetic rationale for SR-T3 and the WT3 protocol framework is developed in the sustained-release T3 complete guide.

For researchers building the SR-T3 component of the stack, the Wilson's SR-T3 Combo Kit is the classical reference product - formulated specifically for the cyclic T3 protocol context. The SRT3-15 entry-strength product is the common starting point for researchers transitioning from immediate-release Cynomel or Cytomel who are calibrating their protocol baseline before moving up the titration ladder.

Component 2: 3,5-T2 (with T3)

T2 - 3,5-diiodothyronine - is the direct mitochondrial activator. Understanding why it belongs in the stack requires understanding a mechanism that post-dates most of the bioenergetic framework's foundational writing: the cytochrome c oxidase binding that Goglia and colleagues documented in 1994.

T3 acts genomically. It binds nuclear thyroid hormone receptors (TRalpha and TRbeta), which then regulate the transcription of genes encoding mitochondrial proteins and electron transport chain enzymes. This is a structural, capacity-building effect operating over hours to days: T3 builds mitochondrial machinery by driving gene expression. What T3 does not do is directly and acutely activate the cytochrome c oxidase enzyme already present in the cell.

That is what T2 does. 3,5-T2 binds directly to subunit Va of cytochrome c oxidase (Complex IV of the mitochondrial electron transport chain) in a non-genomic, rapid-acting mechanism that drives aerobic respiration on a minutes timescale. This is a distinct signal from T3's nuclear receptor action - it is not a prohormone effect, not a genomic effect, and not dependent on new protein synthesis. It is a direct enzyme-level activation of the terminal step in the mitochondrial electron transport chain.

The second reason T2 belongs in the stack is the conversion bottleneck. T2 is produced from T3 by the DIO1 deiodinase enzyme - the same enzyme that converts T4 to T3 and that is impaired in the chronic-illness population by selenium deficiency, elevated cortisol, and inflammatory cytokines. A research subject whose DIO1 is impaired cannot reliably generate adequate T2 from supplemented T3, regardless of how much T3 substrate is available. This is the T3 protocol plateau mechanism: T3 is present for nuclear receptor signaling, but the cytochrome c oxidase-direct pathway is underactivated because DIO1 cannot complete the T3→T2 conversion step. Direct T2 supplementation bypasses this bottleneck by the same logic that direct T3 supplementation bypasses the T4→T3 bottleneck. The full deiodinase dysfunction mechanism and the plateau pattern are analyzed in the T3-to-T2 conversion problem and deiodinase dysfunction guide.

Research-grade T2 is typically delivered paired with T3 in a sustained-release formulation, which is the design rationale behind the Wilson's T3+T2 Combo. Both hormones are delivered in the same HPMC + MCC matrix, providing T3 for nuclear receptor signaling and T2 for direct cytochrome c oxidase activation in a single product designed for researchers addressing both stages of the deiodinase conversion failure simultaneously.

Component 3: Cyproheptadine

Cyproheptadine is the anti-serotonin lever of the stack - and its inclusion follows directly from the bioenergetic framework's most distinctive and least mainstream argument: that serotonin, far from being a "happiness molecule," is a peripheral stress hormone that actively suppresses metabolic rate.

The mechanism is documented. Elevated peripheral serotonin - produced by enterochromaffin cells in the gut under conditions of reduced oxidative phosphorylation and metabolic stress - produces a cascade of effects the bioenergetic framework classifies as metabolic suppressors: vasoconstriction, cortisol amplification via 5-HT2A receptors on adrenal cortex tissue, platelet aggregation, and direct inhibition of mitochondrial Complex I electron transport. The self-reinforcing feedback loop this creates - metabolic suppression drives serotonin elevation, serotonin elevation deepens metabolic suppression - is precisely the cycle that cyproheptadine interrupts. It does so by blocking the 5-HT2A and 5-HT2C serotonin receptors directly, without increasing serotonin synthesis, without reuptake inhibition, and without the dopamine antagonism that makes atypical antipsychotics inappropriate as bioenergetic-protocol compounds.

Cyproheptadine's dual mechanism - H1 histamine antagonism plus 5-HT2A/5-HT2C serotonin antagonism - is pharmacologically specific to what the bioenergetic framework requires. The 5-HT2A blockade addresses vasoconstriction, cortisol amplification, and the serotonin-driven resistance to T3 signaling simultaneously. The H1 blockade adds an anti-inflammatory and anti-vasoconstrictive complement via the histamine pathway. The result is a pharmacological profile that clears the serotonin-driven resistance to the T3 and T2 components of the stack, creating a cellular environment that is more receptive to the metabolic signals those hormones carry.

The bioenergetic research community uses cyproheptadine at dose ranges from 2 mg (sleep-support entry, evenings only, during initial H1 sedation tolerance development) to 4 mg standard anti-serotonin dose (one to two times daily after sedation tolerance develops) through 8-12 mg in higher-range research contexts. The available product is formulated at 4 mg per tablet in 50-tablet bottles - the standard anti-serotonin research dose increment. The complete cyproheptadine mechanism, dose-range discussion, tolerability profile, and bioenergetic-stack context are covered in the cyproheptadine anti-serotonin research guide. The research reference product is the Cyproheptadine 4mg (50 Tablets).

The Cleanest Excipient Profile: Why HPMC + MCC Matters

Peat's framework included a position that mainstream pharmaceutical practice rarely addresses: the critique of excipients. Most common pharmaceutical excipients - the inactive ingredients that constitute the bulk of any tablet or capsule - include agents that fall into categories the bioenergetic framework treats with significant concern. Seed-oil-derived PUFA carriers (commonly used as lubricants and solubilizers), allergen-class proteins (commonly used as binders in tablet compression), and synthetic dyes are present in the majority of off-the-shelf pharmaceutical preparations. For research subjects working within a framework that treats PUFA exposure as a primary driver of mitochondrial membrane peroxidative damage and lipid peroxidation-derived mitochondrial toxicity, the excipient profile of a daily-use research compound is not a trivial concern.

The HPMC + MCC excipient profile - hydroxypropyl methylcellulose plus microcrystalline cellulose - is the cleanest pharmaceutical-grade formulation profile available for sustained-release matrix capsules. HPMC is a non-ionic cellulose polymer: no PUFA origin, no protein content, no allergen classification, derived from plant cellulose and modified with ether groups that confer its hydrophilic gel-forming properties. MCC is a purified, partially depolymerized cellulose: inert, non-absorbable, no PUFA content, no protein content. The two together provide the matrix that controls sustained-release dissolution while adding zero pharmacologically active or PUFA-derived components.

The SR-T3 and SR-T3+T2 catalog uses this HPMC + MCC profile exclusively - no seed-oil-derived lubricants, no allergen-class binders, no dyes. For research subjects whose protocol framework specifically targets the mitochondrial damage associated with PUFA accumulation and lipid peroxidation, the excipient profile of their daily thyroid reference compound is the starting point for applying that framework consistently.

How the Stack Integrates with Strategic Fasting

The full bioenergetic stack - SR-T3 + T2 + cyproheptadine - does not operate in isolation from the other protocol elements the research community discusses. One of the most mechanistically significant integrations is with strategic fasting, which has emerged as an actively reconsidered component of the bioenergetic framework in the community's current discussion.

Peat opposed fasting on cortisol grounds: caloric restriction elevates cortisol, cortisol suppresses DIO1 deiodinase, DIO1 suppression reduces T3 production, and reduced T3 is the opposite of metabolic optimization. That argument is sound for unsupplemented research subjects relying on endogenous T3 production. For research subjects on stable exogenous SR-T3, the mechanism changes: the T3 arriving from outside the deiodinase axis is not gated by DIO1 activity, and cortisol's suppression of that enzyme does not reduce the T3 supply the way it does for subjects whose T3 is endogenously generated.

This opens the fasting calculus to the autophagy and mitochondrial biogenesis benefits - AMPK/SIRT1/PGC-1alpha-driven creation of new mitochondria and AMPK/mTOR/ULK1-driven cellular clearance of damaged organelles - that fasting activates and that Peat's framework could not access without accepting the cortisol cost. T2 adds a further dimension: fasting's biogenesis creates more cytochrome c oxidase complexes per cell, and T2's direct cytochrome c oxidase binding activates those complexes immediately. The combination targets nuclear thyroid signaling (T3), mitochondrial biogenesis (fasting), mitochondrial activation (T2), serotonin suppression (cyproheptadine), and autophagy (fasting) simultaneously - a multi-node approach that addresses the metabolic suppression cascade at more points than the stack or fasting alone could target.

The full mechanistic case for strategic fasting in the bioenergetic framework is developed in the bioenergetic case for strategic fasting beyond Ray Peat. The specific T2 mechanism and why it changes the fasting argument are analyzed in Ray Peat's anti-fasting position reconsidered with T2.

Sourcing: Research-Grade vs Grey-Market

The sourcing landscape for the bioenergetic community's thyroid compounds has changed substantially since the Cynomel-and-Mexican-pharmacy era. The case for research-grade reference standards over grey-market sourcing is not primarily about legal risk - it is about dose accuracy, purity verification, and formulation quality.

Grey-market liothyronine - whether Cynomel from Mexican pharmacy export channels, Cynoplus, or the various online T3 products that circulate in research forums - carries a quality uncertainty that is incompatible with precision protocol work. Authentic Grossman's Cynomel was a real pharmaceutical product with consistent dose accuracy during its peak availability window, but the modern supply chain has degraded significantly: counterfeit products bearing the Cynomel name circulate in online channels, manufacturing pauses have created supply gaps, and Mexican pharmacy export restrictions have tightened. Without HPLC verification per batch, any liothyronine product sourced from unverified channels is pharmacologically uncharacterized. A research subject who calibrates a protocol on an authentic batch and then sources a counterfeit batch is running an undefined dose. The full sourcing discussion, including the Cynomel supply chain history and the pharmacokinetic case for SR-T3 as the modern alternative, is in the Cynomel and Cynoplus Mexican T3 sourcing research post.

Research-grade reference standards provide what the grey-market cannot. HPLC-verified purity and dose accuracy per batch means every capsule is manufactured from characterized API and tested for potency. The excipient profile (HPMC + MCC) is documented and clean. The supply is stable, not dependent on Mexican export channels or customs enforcement variability. And the formulation - sustained-release rather than immediate-release - addresses the pharmacokinetic limitation of Cynomel and Cytomel at the formulation level rather than requiring dose-splitting workarounds to manage the spike.

For the cyproheptadine component, research-grade sourcing matters for the same quality reasons: verified active ingredient at the stated 4 mg per tablet dose, clean excipient profile, consistent tablet manufacture. The grey-market antihistamine supply introduces the same dose-accuracy uncertainty as grey-market liothyronine - a problem that is irrelevant with research-grade reference standards.

Customs and International Shipping Note

All orders from the Chronic Illness Store ship with plain-label discreet international packaging. The plain-label format omits product identifiers on the outer packaging, reducing customs inspection triggers. Shipping details, delivery timelines, and import considerations for specific destination countries are covered at /shipping. For questions about the research-use designation and legal terms that govern all orders, see the FAQ legality section. The Chronic Illness Store representative team handles customs inquiries for in-transit orders.

Frequently Asked Questions

What is the Ray Peat thyroid stack?

The Ray Peat thyroid stack, as converged on by the bioenergetic-research community after years of protocol iteration, is a three-component combination: sustained-release T3 (SR-T3), 3,5-diiodothyronine (T2), and cyproheptadine. SR-T3 provides nuclear thyroid receptor activation while avoiding the spike-and-trough pharmacokinetic profile of immediate-release liothyronine. T2 provides direct cytochrome c oxidase activation at the mitochondrial level, bypassing the DIO1 deiodinase conversion bottleneck that limits endogenous T2 production. Cyproheptadine provides 5-HT2A and 5-HT2C serotonin receptor antagonism, removing the serotonin-driven metabolic brake that would otherwise blunt the response to both thyroid hormones. The stack reflects the bioenergetic framework's core logic: bypass conversion bottlenecks, target the active mitochondrial mechanism directly, and remove the counter-regulatory signals that work against metabolic restoration.

Why does the stack include T2 alongside T3?

T3 and T2 act on distinct and non-overlapping mechanisms. T3 binds nuclear thyroid hormone receptors (TRalpha and TRbeta) and drives genomic upregulation of mitochondrial enzyme expression - a structural, capacity-building effect operating over hours to days. T2 binds cytochrome c oxidase subunit Va directly and acutely elevates aerobic respiration in a non-genomic, minutes-scale mechanism that T3's nuclear pathway cannot replicate. More practically, the DIO1 enzyme that would ordinarily convert supplemented T3 to T2 is impaired in the chronic-illness population by the same selenium deficiency, elevated cortisol, and inflammatory cytokines that impaired the upstream T4→T3 conversion step. A T3-only protocol provides substrate for nuclear receptor signaling while leaving the cytochrome c oxidase-direct pathway substantially underactivated - the mechanistic explanation for the T3 protocol plateau the community documents. Direct T2 supplementation bypasses the conversion bottleneck, providing the mitochondrial activation signal that endogenous DIO1 cannot reliably produce.

Why include cyproheptadine in a thyroid stack?

Cyproheptadine addresses the serotonin-driven metabolic suppression that would otherwise blunt the response to T3 and T2. In the bioenergetic framework, elevated peripheral serotonin - a marker of reduced oxidative phosphorylation and chronic metabolic stress - inhibits mitochondrial Complex I, amplifies cortisol release from the adrenal cortex via 5-HT2A receptor activation, and promotes the inflammatory signaling that further suppresses DIO1 deiodinase activity. This serotonin-driven resistance to T3 signaling means that administering T3 into a high-serotonin cellular environment produces a blunted and inconsistent response. Cyproheptadine's 5-HT2A and 5-HT2C antagonism removes this resistance - clearing the metabolic brake simultaneously with the thyroid hormones pressing the accelerator. The research community consistently reports that the cyproheptadine plus T3 combination produces more sustained metabolic response than T3 alone, an outcome the mechanistic complementarity predicts.

What dose strengths does the SR-T3 line come in?

The SR-T3 catalog covers five dose strengths: 7.5, 15, 22.5, 45, and 90 mcg. This range is designed to cover the complete Wilson's WT3 titration ladder - from the initial entry dose of 7.5 mcg twice daily through the higher-dose phases used in the latter stages of the titration cycle. Having five calibrated steps available allows researchers to move through the titration schedule without improvising mid-range doses by cutting tablets, which undermines the dose-accuracy advantage of HPLC-verified research-grade formulation. The SRT3-15 entry-strength product at 15 mcg is the most common starting point for researchers transitioning from immediate-release T3 products. The Wilson's SR-T3 Combo Kit bundles the dose strengths for the complete WT3 protocol cycle.

Is the Wilson's T3+T2 Combo aligned with the Ray Peat framework?

Yes - the Wilson's T3+T2 Combo addresses both the T4→T3 and the T3→T2 deiodinase conversion failures that the bioenergetic framework identifies as central to the chronic-illness metabolic picture. It delivers sustained-release T3 for nuclear thyroid receptor signaling - the direct-T3 approach that Peat's framework established as correct over the T4-only levothyroxine model - and adds sustained-release T2 for direct cytochrome c oxidase activation, the downstream mitochondrial mechanism that the T2 literature post-dating Peat's major writings makes available. The HPMC + MCC excipient profile aligns directly with the Peat-framework critique of PUFA-derived and allergen-class pharmaceutical excipients. The combination is best understood as the bioenergetic community's most complete thyroid research product: Peat's T3 insight carried through to its mitochondrial activation endpoint, with the deiodinase bypass logic applied at both conversion steps.

How is this stack different from a single-compound protocol?

Single-compound protocols target one node of the metabolic suppression cascade while leaving the others active. T3 alone drives nuclear receptor signaling but leaves the cytochrome c oxidase-direct pathway dependent on DIO1 activity that is typically impaired - explaining the T3 plateau. T2 alone activates the mitochondrial enzyme directly but leaves the nuclear receptor signaling pathway and the serotonin-driven metabolic resistance unaddressed. Cyproheptadine alone removes the serotonin brake but provides no thyroid hormone substrate for nuclear receptor or mitochondrial activation. The three-component stack addresses the nuclear receptor signal (T3), the mitochondrial activation signal (T2), and the metabolic brake removal (cyproheptadine) simultaneously. The community-documented consistency advantage of the combined stack over single-compound protocols reflects this three-node targeting - each component is addressing something the other two leave unaddressed.

Where can I find research-grade T3+T2 and cyproheptadine?

Research-grade SR-T3, T3+T2 combination, and cyproheptadine are available directly through this site. The Wilson's T3+T2 Combo provides sustained-release T3 and T2 together in HPMC + MCC matrix, formulated for the full bioenergetic stack application. The Wilson's SR-T3 Combo Kit covers the WT3 titration ladder for researchers focusing on the SR-T3 component. The Cyproheptadine 4mg (50 Tablets) is the reference anti-serotonin product at the standard 4 mg per tablet dose. All products are HPLC-verified for potency and purity, formulated in the HPMC + MCC excipient profile, and shipped with plain-label discreet international packaging. The complete research compound catalog is available at /catalog.

Does the stack work with intermittent fasting?

The combination of SR-T3 and T2 is mechanistically well-suited to pairing with strategic fasting in ways that Peat's original anti-fasting framework did not anticipate. SR-T3's HPMC matrix formulation does not require food intake for absorption, so the flat serum T3 curve it produces is maintained through a fasting window without disruption. T2's direct cytochrome c oxidase activation targets precisely the mitochondrial enzyme complexes that fasting's AMPK-driven biogenesis creates - a structural capacity built by fasting, activated acutely by T2. And cyproheptadine's anti-serotonin action continues regardless of fed or fasted state. The full mechanistic case for strategic fasting combined with the SR-T3 + T2 stack is in the bioenergetic case for strategic fasting beyond Ray Peat and Ray Peat's anti-fasting position reconsidered with T2.

Closing Note

The Ray Peat-aligned thyroid stack - SR-T3 for nuclear receptor activation, T2 for direct cytochrome c oxidase activation, cyproheptadine for serotonin receptor blockade - is the architecture the bioenergetic research community has arrived at after years of protocol iteration and documented community experience. Each component is individually mechanistically justified. The combination is justified by the multi-node structure of the metabolic suppression cascade that no single compound can address alone.

For researchers ready to build this stack from research-grade reference standards: the Wilson's SR-T3 Combo Kit covers the SR-T3 WT3 titration ladder, the Wilson's T3+T2 Combo is the most complete single thyroid research product for addressing both conversion bottlenecks simultaneously, and the Cyproheptadine 4mg (50 Tablets) is the anti-serotonin component. All products are HPLC-verified, formulated in the clean HPMC + MCC excipient profile, and available in the complete bioenergetic-framework research catalog.