A nine-amino-acid hormone made by the thymus that needs zinc to work; tested in 1980s autoimmune trials, never approved.
Also called FTS (facteur thymique serique), Serum thymic factor, Zinc-FTS, FTS-Zn, Nonathymulin (synthetic form)
Thymulin is a real human hormone. The thymus, the gland behind the breastbone where T cells mature, releases it into the blood. It is nine amino acids long and only works when a zinc atom is bound to it. French researchers led by Jean-Francois Bach sequenced it from pig blood in 1977. Blood levels fall with age as the thymus shrinks, and they also fall in zinc deficiency.
A synthetic version called nonathymulin went into human trials in France in the 1980s. In two placebo-controlled rheumatoid arthritis trials, 56 percent of patients on 5 mg a day improved on the global assessment versus 17 percent on placebo. A 40-patient multiple sclerosis trial found no benefit. Development stopped, and it was never approved anywhere.
Most current interest comes from animal work. In mice and rats thymulin calmed inflammation by blocking NF-kB, reduced pain and lung blood pressure in disease models, and in a 2026 Nature Communications study it reduced age-related inflammation in immune cells and made tumors respond better to immunotherapy in older mice. The one thing proven in people is narrower: zinc supplements raise thymulin activity in zinc-deficient adults.
What it binds to, and what happens inside the body after that, step by step.
Thymulin binds zinc in a 1:1 ratio, and only the zinc-bound form is biologically active. It acts on immature T cells and on immune cells such as macrophages, where it blocks the NF-kB pathway and lowers production of inflammatory signals like IL-1, IL-6, and TNF-alpha. It also signals back to the pituitary, affecting growth hormone, prolactin, and reproductive hormones in animal studies. A specific thymulin receptor has not been fully characterized.
Human results and animal results are kept apart below. A result in rats tells you a mechanism is plausible. It does not tell you what happens in a person.
Thymulin has small placebo-controlled human trials, but they are from the 1980s and point both ways: improvement in rheumatoid arthritis, no effect in multiple sclerosis. Nothing since has tested it as a treatment in people. Its anti-inflammatory and anti-aging effects are shown in mice and rats, and the human data that hold up today are about zinc supplements raising thymulin levels.
Adults with rheumatoid arthritis, two randomized trials testing 1, 5, and 10 mg/day
At 5 mg/day, 56 percent improved on global assessment versus 17 percent on placebo (p < 0.02), with minimal side effects and no clear change in immune lab tests.
Read the study40 patients with active, moderately disabling multiple sclerosis, 6 months of treatment
No difference from placebo on Kurtzke disability, Ambulation Index, or Functional Scale; no significant side effects.
Read the study27 Crohn's disease patients in remission randomized to zinc sulfate 60 mg, 200 mg, or placebo for 3 months
Only 200 mg/day zinc sulfate raised plasma zinc and active thymulin.
Read the study44 institutionalized elderly adults, 16-week crossover, 20 mg zinc a day
Serum zinc rose about 20 percent and serum thymulin activity was partly restored.
Read the studyAged mice with breast tumors, plus human immune cells
Thymulin cut IL-1, IL-6, and TNF-alpha from aged myeloid cells via NF-kB, improved tumor control and survival, and made tumors respond to anti-PD-L1 therapy in older mice.
Read the studyAdult Wistar rats with chemically induced pulmonary hypertension
100 ng/kg a day under the skin for 3 weeks prevented the structural, pressure, and inflammatory changes; the zinc vehicle alone had part of the effect.
Read the studyBlood immune cells from healthy volunteers and lupus patients
At 1,000 ng/ml thymulin lowered TNF-alpha release from both groups' cells; effects on IL-1 went in opposite directions in healthy and lupus cells.
Read the studyThese are questions the published research has not answered.
No product containing Thymulin is approved as a medicine by the FDA.
The synthetic form, nonathymulin, was tested in French trials in the 1980s and never approved. Homeopathic products labeled thymulin are extreme dilutions and contain essentially no peptide; they are not the same thing. Not named on the WADA list, but injected synthetic thymulin falls under S0 (non-approved substances), banned in and out of competition.
No human half-life has been published for Thymulin, so we do not draw a clearance curve. Half-lives quoted online for it are usually estimates from animal data.
This table records the doses that trials and approved labels used, with the source for each row. It is a record of research, not a recommendation, and it is open to free members.
Which symptoms are expected and which mean stop and get help: side effects and red flags.
Tap a claim to see what the studies found.
Thymic peptides changed hair growth in human scalp follicles kept alive in a dish, with different peptides pushing in different directions. There is no clinical trial in hair loss.
It falls with age and gene therapy restored some hormone effects in thymus-deficient mice. No human study has measured thymus size or new T-cell output after thymulin.
In zinc-deficient groups, supplements raised active thymulin: 20 mg a day in elderly adults and 200 mg a day of zinc sulfate in Crohn's patients.
Small 1987 trials showed benefit in rheumatoid arthritis; a 1989 multiple sclerosis trial showed none. It was never developed further or approved.
Homeopathic dilutions are diluted so far that essentially no peptide remains; the hormone studies used the actual peptide.
These pairings come up often. Almost none have been tested together in a trial, and the evidence note on each says so plainly.
Both come from the thymus and are discussed for immune aging.
EvidenceThey have been compared in lab work such as scalp follicle cultures, but never given together in a human study.
No published stability study for current products. Labs generally keep freeze-dried peptides frozen at about -20 C, dry and away from light.
No published stability data in solution. Activity depends on zinc binding, which the solution's contents can affect; labs typically refrigerate and use promptly.
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