# Thymulin: The Zinc-Powered Thymic Nonapeptide, Decoded > Thymulin is a zinc-dependent thymic nonapeptide that goes from inert to active the instant one zinc ion binds 1:1. A bold, fully cited digest of what the immune, anti-inflammatory, and lung studies actually measured. Here is the wild part: the peptide is dead until one zinc ion clicks into place — then it powers up. We read the published studies straight, lead with the numbers, and call out every honest gap. ## The short version Thymulin is a small hormone made by the thymus, the immune-training gland tucked behind your breastbone. It is a nonapeptide (a chain of nine amino-acid building blocks), and here is its signature trick: it only switches on when one zinc atom is attached. Strip the zinc away and the molecule goes inert; add it back and activity returns [1]. In animal and lab studies, the zinc-bound form has shown effects on T cells (the immune system's trained defender cells), on inflammation, and across several lung models. Thymulin is a research peptide — not a supplement, not a drug, and not FDA-approved for anything. ## What the thymulin literature actually shows Thymulin (serum thymic factor; FTS / FTS-Zn) is a zinc-dependent thymic nonapeptide hormone, sequence pyroGlu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn, made exclusively by thymic epithelial cells (the gland's lining cells that build it) [2]. Its defining fact is mechanical and absolute: the peptide is biologically active only when bound to zinc in a 1:1 molar ratio, and the zinc-free apopeptide does nothing [1]. That single zinc ion is the whole power-up. The research record reads like a stack of action panels. In a 1982 assay, chelating zinc out of the molecule with Chelex abolished its activity, and adding zinc back restored it — the result that earned the active form its name, thymulin [1]. In humans with mild zinc deficiency, circulating thymulin activity dropped even with normal plasma zinc and bounced back with zinc repletion [3]. In mice, thymulin lowered pro-inflammatory signals and dialed down the NF-kB pathway, a master switch that turns inflammation genes on [6]. And in one of the loudest findings in the whole literature, a single inhaled dose of thymulin-gene nanoparticles — given after asthma was already established — normalized key lung pathology in mice at 20 days [7]. None of that is a human treatment. Every result below is described as what was measured, in which species, with the citation right there. That is the entire job of this site: surface the findings, lead with the number, and keep the honest caveats loud. The [thymulin research findings](/research) page lays out the mechanism and the key studies; [why thymulin needs zinc](/zinc-dependence) goes deep on the activation switch. ## Thymulin peptide: a zinc-dependent thymic nonapeptide The thymulin peptide is nine amino acids long with the sequence pyroGlu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn (molecular formula C33H54N12O15, molecular weight roughly 858.9 Da, CAS 63958-90-7) [2]. It is endogenous — your body already makes it. Thymic epithelial cells secrete it from birth; levels peak in childhood and decline with age and with falling zinc status [2][3]. When a single zinc ion binds, the peptide folds into a specific active conformation that NMR studies can detect [2]. That zinc-bound shape is what classical assays score as biological activity, and what drives the T-cell differentiation thymulin is best known for [2]. Handled in the lab, thymulin is a research peptide — distinct from thymosin alpha-1, thymosin beta-4, and thymopentin, which are separate compounds with their own data. Conflating them is the single most common error in consumer write-ups, and this digest does not make it [4]. ## What the research describes: thymulin peptide effects studied in models Across animal and in-vitro models, thymulin peptide benefits reported in the literature cluster into a few clean beats — and every one is a model finding, never a human claim. On the immune side, thymulin drives T-lymphocyte differentiation and, in chickens, enhanced lung natural-killer-cell cytotoxicity against a virus in a dose-dependent way [13]. On the anti-inflammatory side, in LPS-treated mice it lowered plasma pro-inflammatory cytokines and inducible heat-shock proteins while modulating NF-kB and SAPK/JNK signaling [6]. The dealt lens for this digest is the lung. In mice, a single intratracheal dose of thymulin-expressing plasmids reversed established experimental-asthma pathology at 20 days [7], and in rats, thymulin attenuated monocrotaline-induced pulmonary hypertension by modulating interleukin-6 and suppressing the p38 pathway [8]. The full [thymulin lung research](/lung-research) page breaks those down panel by panel. Thymulin also acts on the neuroendocrine system as a hypophysiotropic peptide (one that signals the pituitary gland), part of a bidirectional thymus-neuroendocrine axis [4]. Big picture: large effect beats in models, a thin human record, and a mechanism that is unusually well defined for a peptide this size. For the amounts researchers actually administered, see [thymulin dosage in studies](/dosage). ## What is thymulin? Thymulin (serum thymic factor; FTS / FTS-Zn) is a zinc-dependent thymic nonapeptide hormone produced exclusively by thymic epithelial cells and biologically active only when bound to zinc in a 1:1 ratio [1][2]. It is studied as a research peptide and is not FDA-approved for any use. It is endogenous, declines with age and zinc deficiency, and is chemically distinct from other thymic peptides [4]. For the synonyms, the zinc switch, and the data, start with [why thymulin needs zinc](/zinc-dependence) and the [thymulin research findings](/research). ## The honest status, up front CAREFUL — read this before anything else. Thymulin is not FDA-approved for any human indication and is handled as a research peptide for laboratory use only. It is not a dietary supplement. The strong findings here are preclinical — cell and animal models — plus a small, dated set of human observations, and several historical human studies used a synthetic analog (nonathymulin), not native thymulin. Because activity is strictly zinc-dependent, thymulin-specific effects are entangled with zinc status, which complicates interpretation. Nothing on this site is dosing guidance, medical advice, or an endorsement. See the [frequently asked questions about thymulin](/faq) for the plain-English version. --- A high-energy reading of the thymulin record drawn panel by panel — the zinc power-up that switches the nonapeptide on, the T-cell and lung findings, and the missing human trials all inked from the published studies; no clinic behind the page and nothing here dosed, dispensed, or sold.