# Thymulin FAQ: Identity, Zinc, Safety, and Regulatory Status

> Thymulin FAQ: what it is, why it needs zinc, whether it is FDA-approved or a supplement, how it is administered in research, and how it differs from thymosin alpha-1 — answered from the record.

Direct answers on identity, the zinc requirement, safety, dosing, and regulatory standing — each drawn from the cited literature, none offered as medical advice.

## What is thymulin?

Thymulin is a zinc-dependent thymic nonapeptide hormone with the sequence pyroGlu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn, produced by thymic epithelial cells and biologically active only when bound to zinc in a 1:1 ratio [1][2]. It was named in 1982 for the zinc-bound active form of serum thymic factor. It is studied as a research peptide and is not approved for human use.

## What is thymulin peptide?

Thymulin peptide is the nine-amino-acid thymic hormone formerly called serum thymic factor (FTS) [1]. It is studied as a research peptide and is active only as the zinc-bound form; the zinc-free apopeptide is inactive [2]. Its molecular weight is near 858.86 Da and its CAS number is 63958-90-7.

## Is thymulin the same as serum thymic factor (FTS)?

Yes. FTS — *facteur thymique sérique* — is the original name, and the term "thymulin" was coined for the zinc-bound, biologically active form of the same peptide once the zinc requirement was established [1]. In the literature, FTS, Zn-FTS, and thymulin all refer to the same nonapeptide.

## Why does thymulin need zinc to work?

Zinc binding gives thymulin its active three-dimensional conformation; the zinc-free apopeptide is inactive [1][2]. Chelating the zinc abolishes activity in the rosette assay, and adding zinc back restores it, optimally at a 1:1 metal-to-peptide ratio [1]. Zinc is effectively the molecule's on-switch, not an optional cofactor.

## What is the amino acid sequence of thymulin?

Thymulin is the linear nonapeptide pyroGlu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn (written <Glu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn), active only when bound to one zinc ion in a 1:1 molar ratio [2]. The zinc-bound form adopts a specific conformation detectable by NMR, which the apopeptide does not.

## What does thymulin do in the body?

Endogenously, thymulin drives T-lymphocyte differentiation and acts as a hypophysiotropic peptide within a two-way thymus-neuroendocrine axis [4]. In research models it also shows anti-inflammatory activity, including suppression of NF-kB signalling [6]. These are described findings, not demonstrated human treatments.

## Does thymulin boost the immune system?

In research models thymulin promotes T-cell maturation and modulates immune-cell function, and its activity falls with zinc deficiency and with age [3][11]. In vitro it corrected T-cell immaturity in malnourished children's lymphocytes [8]. This is preclinical and ex-vivo evidence, not a demonstrated human immune treatment.

## Does thymulin reduce inflammation?

In animal models thymulin lowered pro-inflammatory cytokines and suppressed NF-kB and SAPK/JNK signalling — for example in LPS-treated mice given thymulin before the challenge [6]. These are research findings in study species, not a demonstrated anti-inflammatory therapy for people.

## What are the benefits of thymulin?

In study models thymulin has been associated with T-cell differentiation, reduced inflammatory signalling (including NF-kB suppression), and pituitary and neuroendocrine effects [4][6]. Human benefit is not established. These are research findings, not outcomes demonstrated in adequate human trials.

## What are the benefits of thymulin peptide?

Research describes immune-modulating, anti-inflammatory, and neuroendocrine effects of the thymulin peptide in animal and in-vitro models [4][6][8]. These are study findings, not established human benefits, and thymulin is not approved for any indication.

## Can thymulin help with autoimmune disease?

Thymulin reduced disease severity in rodent autoimmune-neuroinflammation work and, in vitro, normalized abnormal T-cell subset markers on lymphocytes from rheumatoid-arthritis and lupus patients [4][12]. An open FTS-Zn trial in rheumatoid arthritis reported immunological modulation [9]. These are research findings, not a human autoimmune treatment.

## How is thymulin different from thymosin alpha-1?

They are distinct molecules. Thymulin is a zinc-dependent nonapeptide; thymosin alpha-1 is a different, longer thymic peptide with its own sequence, mechanism, and literature [1]. Their data do not transfer between them, and consumer sources that treat them as one are mistaken.

## Is there a thymulin supplement?

No. Thymulin is not a dietary supplement and there is no recognized thymulin supplement product. It is handled as a research peptide for laboratory use. Note that serum thymulin activity tracks zinc status, but that is a property of the body's own thymulin, not a supplement claim [3].

## Is thymulin FDA approved?

No. Thymulin is not approved by the FDA for any indication and is not a dietary supplement; it is handled as a research peptide for laboratory use only. There is no approved human thymulin product of any kind.

## Is thymulin legal to buy?

Thymulin is not a US controlled substance, but it is not approved for human use; research suppliers offer it for laboratory research only. It is not a dietary supplement. Athletes should note that peptide hormones and immunomodulators are scrutinized in sport and should consult current WADA guidance.

## What are the side effects of thymulin?

There is no characterized human side-effect profile for thymulin. Early human trials used synthetic analogs (nonathymulin), and a topical pilot was preliminary; thymulin is not approved for human use. See [thymulin side effects](/side-effects) for the full reading of the safety record.

## What are the side effects of thymulin peptide?

The thymulin peptide's human safety data are sparse and dated, and there is no rigorous adverse-event profile. A topical zinc-thymulin pilot reported its preparation as well tolerated, but it was small, single-line in its safety reporting, and low-tier. The accurate position is that thymulin peptide side effects are uncharacterized.

## Is thymulin safe?

Thymulin's human safety is not established. Most evidence is preclinical, the human data are limited and dated, and it is handled as a research chemical for laboratory use only. Neither "safe" nor "dangerous" is supported; the question is simply unanswered by adequate human study.

## Does thymulin help with hair loss?

A single small open-label pilot studied a topical zinc-thymulin spray in androgenetic alopecia, reported as preliminary and well tolerated. Specific regrowth figures were not independently grounded and should be treated as preliminary. See [thymulin and hair loss](/hair-loss) for the full reading.

## What is the dosage of thymulin peptide?

There is no established human dosage of thymulin peptide; it is a research peptide. Reported doses are study findings in animal models — for example 50 µg per mouse intraperitoneally, or 10-50 ng per 100 g in chickens — not protocols for people [13][15]. See [thymulin dosage in research](/dosage) for the full register.

## How is thymulin administered in research?

In published studies, routes include intraperitoneal, subcutaneous, intracerebroventricular, intratracheal (for gene therapy), and direct in-vitro incubation [4][7][13][14]. In humans, only limited and dated work used analogs or FTS-Zn, plus one topical pilot. There is no approved human injectable thymulin product.

## Is thymulin taken as an injection?

Most research used parenteral routes — subcutaneous and intraperitoneal — in animals [13][14]. There is no approved human injectable thymulin product; it is handled as a research peptide for laboratory use. This site does not provide administration guidance for people.

## Are there reviews or experiences of thymulin?

Public discussion is thin; thymulin is a niche research peptide with limited human study. This site summarizes the published literature rather than user experiences or product reviews. Where a human-facing claim exists — such as the topical hair-loss pilot — it is read as preliminary against its source.

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A finely-kept specimen cabinet of the thymulin literature — the zinc-bound thymic nonapeptide catalogued from a thin, dated record, its established findings engraved beside its open gaps and the molecule held distinct from thymosin alpha-1 and thymalin; a heritage archive, not a clinic, a vendor, or a prescription.