The question has been asked in bioenergetic and thyroid research forums more or less continuously since about 2020, across threads that now run to many pages, and it has never received a clean answer.
This piece separates what is documented from what is inference, because those two categories have become badly mixed in the available discussion, and because the practical decision facing anyone still waiting depends entirely on which is which.
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SRT3-15 Slow Release T3 (15mcg)
The short version: there has been no formal discontinuation notice. Cynomel's absence has been reported as production delay rather than withdrawal. But the last lots widely reported in circulation carried a September 2025 expiry, the availability pattern has been deteriorating for roughly five years rather than stabilising, and no credible reappearance date has surfaced. The honest reading is that waiting is not a strategy with a defined endpoint.
The broader history of Grossman's thyroid line and the counterfeit problem it created is covered in the Cynomel and Cynoplus sourcing analysis. The replacement options are compared in the Cynoplus alternatives guide and the four-brand comparison.
What Is Actually Documented
Stripping out speculation, the reportable position is narrow.
| What | Status |
|---|---|
| Formal discontinuation notice | None located |
| Reported cause of absence | Production delay |
| Reported return date | None given |
| Last widely reported lots | September 2025 expiry |
| Availability pattern | Intermittent for roughly 5 years, effectively absent through 2025 |
| Pharmacy catalogue listings | Still present, availability not confirmed |
| Manufacturer trading status | Unverified |
That last row deserves emphasis. The claim that Laboratorios Grossman has ceased operating circulates widely and is stated with confidence in forum threads. No primary source supporting it was located. It may be true. It is not established, and repeating it as fact is how forum inference becomes forum folklore.
The distinction between "production delay" and "discontinued" is not pedantry. A delayed product has a manufacturer with an intention to resume. A discontinued product does not. Everything publicly reported points to the former description being used, and nothing publicly reported confirms it is still accurate.
The Timeline, As Far As It Can Be Dated
Piecing together a chronology from community reporting is imperfect, because forum posts date the moment someone noticed a problem rather than the moment it began. With that caveat, the sequence is consistent enough across independent threads to be worth setting out.
| Period | Reported position |
|---|---|
| Through the 2010s | Widely available and cheap; becomes the community default T3 source |
| From around 2020 | Availability turns intermittent; long forum threads open asking whether production has stopped |
| 2022 onward | Tightened export handling and customs enforcement reported; counterfeit concerns surface |
| Early 2025 | Reported unavailable due to production delays, with no return date given |
| Mid 2025 | Remaining circulating lots reported carrying September 2025 expiry |
| Late 2025 onward | No confirmed resupply reported; catalogue listings persist without fulfilment |
What that shape shows is a slow degradation rather than a sudden stop. The gaps lengthened over five years, which is a different pattern from a temporary manufacturing interruption and is the main reason the optimistic reading has become harder to sustain.
It is worth being explicit that this table is assembled from community reporting, not from manufacturer statements. No manufacturer statement was located at any point in the sequence, which is itself part of the story: a product with an active communications relationship to its users would not have required five years of forum archaeology to establish its status.
Why "It Is Listed On A Pharmacy Site" Proves Nothing
A recurring pattern in these threads is a user posting a link to a Mexican pharmacy page showing Cynomel 25 mcg, 100 tablets, apparently in stock, as evidence that the supply problem has resolved.
Online pharmacy catalogues are not inventory systems. A listing page is created when a product is carried and is very rarely retired when the supply line stops, because retiring it costs staff time and loses search traffic. Pages persist. Some carry a pre-order or backorder flag, which is itself informative, and some do not distinguish at all.
The practical test is not whether a page exists but whether an order placed against it ships, and the reports on that point have been consistently negative through the period in question.
The September 2025 Expiry Matters More Than It Looks
Reports through 2025 indicated that the remaining lots in circulation carried expiry dating to September 2025.
That date is now behind us, and it has a specific consequence: any material currently offered as Cynomel is either expired, or it is not from the lots that were last confirmed to be circulating. Both possibilities warrant scrutiny, and the second is the more concerning of the two.
Scarcity of a sought-after product is one of the documented conditions under which substandard and falsified material enters circulation, alongside informal supply routes and limited post-market surveillance. That combination is summarised in the systematic review cited below and it describes the present situation for Cynomel precisely. A microgram-dose thyroid tablet offers an end user essentially nothing to inspect, so the question of what is actually in a tablet sold under this name in 2026 cannot be answered by looking at it.
This is the part of the problem that persistence does not solve. Continuing to search harder for Cynomel through informal channels increases exposure to exactly the material the scarcity has drawn in.
The Wider Picture Tightened At The Same Time
Cynomel's disappearance would be easier to route around if the rest of the liothyronine supply had been stable. It was not.
- United Kingdom. No general national liothyronine shortage was in effect, but the sole supplier of liothyronine 20 microgram vials was reported out of stock from October 2025 through the end of April 2026. Separately, Tertroxin, the long-standing UK 20 mcg tablet, has been discontinued.
- United States. Liothyronine availability has been intermittent and variable by region, manufacturer and tablet strength, with the position reported as deteriorating across 2023 to 2025 under spillover from levothyroxine supply problems and rising T3 demand.
- Desiccated thyroid. On 7 August 2025 the FDA notified manufacturers, importers and distributors of unapproved animal-derived thyroid products, including Armour Thyroid, NP Thyroid and Nature-Throid, of intended enforcement action, indicating a twelve-month transition window. Approximately 1.5 million Americans received prescriptions for these products in 2024.
The relevant observation is not that any single one of these is catastrophic. It is that the fallback options researchers name for one another have been contracting simultaneously, so advice written even eighteen months ago may reference three alternatives of which two have since moved.
Why Cheap Generics Disappear Quietly
The absence of an announcement confuses people, because a discontinuation feels like the kind of event that ought to be announced. In this category it usually is not, and the reasons are structural rather than sinister.
A low-priced generic in a small national market operates on thin margins across a limited volume. The manufacturer's obligations run to its domestic regulator and its domestic patients. An international research community that discovered the product through informal channels and buys it through pharmacy intermediaries is not a customer the manufacturer is aware of, contracted to, or obliged to notify. From the inside, a decision to pause a low-margin line is a routine production matter. From the outside, in a forum thread on another continent, it looks like an unexplained disappearance.
Several ordinary pressures push in the same direction. Active ingredient sourcing for a small line can become uneconomic. Regulatory requalification costs fall on a product generating little revenue. Equipment servicing gets scheduled around higher-value lines. None of these produce a press release, and any of them can extend from a pause into a permanent stop without a formal decision ever being taken.
This is why "no discontinuation notice" should not be read as encouraging. For a product of this type, the absence of an announcement is the expected condition whether it returns or not. It carries almost no information either way, which is precisely why the availability pattern matters more than the absence of a statement.
The corollary is that any future replacement chosen on the same basis, low price plus informal access, inherits the same exposure. The lesson of the Cynomel sequence is less about which product to move to and more about not rebuilding a protocol on a supply route with no accountable relationship to the people depending on it.
What The Pattern Suggests
Forecasting a specific manufacturer's production decisions from outside is not possible, and this article will not pretend otherwise. What can be observed is the shape of the trend.
Availability has been intermittent for roughly five years, not stable-then-interrupted. The gaps lengthened rather than shortened. No return date has been offered at any point. The last confirmed lots have now expired. And the product's original appeal rested substantially on price and access through a particular channel rather than on any pharmacological property unavailable elsewhere.
That last point is the one most worth sitting with. Cynomel was 25 mcg liothyronine sodium. It was not a unique molecule, a proprietary formulation, or a delivery system nobody else had. It was ordinary immediate-release T3 that happened to be cheap and reachable. The thing that made it valuable was the supply channel, and the supply channel is what failed.
A product defined by its access route cannot be replaced by waiting for that route to reopen. It is replaced by finding a different route to the same molecule.
If You Are Still Waiting
The practical position depends on which product the protocol was built on.
For Cynomel, the molecule is liothyronine sodium at 25 mcg and it is not scarce in general, only through that particular channel. Tiromel matches the strength exactly at 25 mcg per tablet. The four-brand comparison covers the alternatives and their verified specifications.
For Cynoplus, the position is narrower because the T4 component has to be replaced too, and most of the commonly named substitutes are liothyronine only. That decision is worked through in the Cynoplus alternatives guide.
For either, moving to an extended-release formulation addresses a limitation that Cynomel always had rather than merely restoring what was lost. Immediate-release liothyronine produces an early serum peak that extended-release formulations are specifically designed to attenuate, which is the pharmacokinetic argument set out in the sustained-release T3 guide. The SRT3-15 slow release T3 is the common entry strength for researchers transitioning from immediate-release T3, and the full SR-T3 range covers the titration ladder. Where the protocol requires both hormones, the SRT4+T3-120 holds the Cynoplus 120/30 strength and ratio.
Whatever the destination, a brand or formulation change should be treated as a protocol change with a proper assessment interval rather than a seamless swap. A cohort study of a forced dose-equivalent brand switch found measurable movement in plasma thyrotropin even where the substitute was nominally matched on dose.
What The Evidence Establishes, and What It Does Not
Established. No formal discontinuation notice has been located. Absence was reported as production delay. The last widely reported lots carried September 2025 expiry. Availability has been intermittent for approximately five years. Tertroxin is discontinued in the UK. The FDA issued its notification regarding unapproved animal-derived thyroid products on 7 August 2025.
Reported but unverified. That Laboratorios Grossman has ceased operating. This is widely repeated and was not confirmed by any primary source located.
Not established. Whether Cynomel will return, on what timescale, or in what form. Any specific claim about a reappearance date. The provenance or content of material currently offered under the name.
Frequently Asked Questions
Has Cynomel been officially discontinued?
No discontinuation notice has been located. Its absence has been described as production delay, which implies an intention to resume, though no return date has been given at any point and the absence has now run for an extended period.
Is Laboratorios Grossman still in business?
Unverified. The claim that it has ceased operating circulates widely in forum discussion but no primary source supporting it was located. It should be treated as inference rather than fact.
Why do pharmacy sites still list Cynomel?
Because catalogue pages are rarely retired when a supply line stops. A listing demonstrates that a product was once carried, not that an order will ship. Some sites carry pre-order or backorder flags, which are more informative than the listing itself.
Should I buy Cynomel if I find it for sale in 2026?
The last widely reported lots expired in September 2025, so anything currently offered is either past expiry or is not from those lots. Scarcity of a sought-after product is a documented condition for substandard and falsified material entering circulation, and a microgram-dose tablet cannot be verified by inspection.
What is the closest replacement for Cynomel?
Tiromel, at 25 mcg liothyronine per tablet, matches the strength exactly. It is liothyronine only, which is equivalent for Cynomel but not for Cynoplus.
Is the T3 supply problem limited to Mexico?
No. A UK vial supply gap ran from October 2025 to April 2026, Tertroxin has been discontinued in the UK, US availability has been intermittent by strength and manufacturer, and desiccated thyroid faces an FDA enforcement question in the United States. Several fallback routes contracted in the same period.
Will waiting work?
There is no evidence supporting a defined endpoint to wait for. The availability trend has been deteriorating rather than recovering, and the product's appeal rested on a supply channel rather than on any property unavailable in other liothyronine preparations.
Closing Note
The most useful reframing of this question is that it is the wrong question.
"Is Cynomel coming back" treats the product as irreplaceable, when what was actually irreplaceable was the combination of a common molecule, a low price, and a channel that did not ask for a prescription. Two of those three were always contingent, and the contingent parts are the parts that failed.
The molecule itself was never scarce. It is available from multiple manufacturers, in a range of strengths, and in extended-release formulations that did not exist when Cynomel first became the community default. The researchers who resolved this fastest were the ones who stopped tracking a brand and started specifying what they actually needed: liothyronine, at a known dose, from a source that could tell them what was in the tablet.
All compounds discussed here are research chemicals supplied for laboratory research use only. Nothing in this article is medical advice, a treatment protocol, or a recommendation for human or animal consumption. Supply and regulatory status change without notice and the positions described were current at the date of writing. Researchers should consult the primary literature cited below and appropriate qualified professionals.