Thymulin
PeptideThe medical score (22) is low due to the absence of controlled human studies [s9]. The community score (38) is slightly higher because isolated positive expectation reports exist in r/Peptides [c1, c2], which are however based on confusion with thymalin and lack of personal experience [c3]. The divergence is moderately negative, meaning community perception slightly overestimates the clinical evidence.
Unlock full information
Dosages, side effects, studies and more — free after registration.
Register for freeRating Scales
TL;DR
Thymulin is a zinc-dependent nonapeptide with a plausible immunological mechanism, but human evidence is almost entirely absent — available data come predominantly from animal and in vitro studies. In the community it is frequently confused with Thymalin (a thymic polypeptide extract), which further dilutes an already thin evidence base. Reproducible self-reports with clear dosing and outcomes are barely findable. Anyone experimenting here is doing so without clinical guidance — that's worth being upfront about.
Description
Thymulin is a zinc-containing nonapeptide of the thymus that regulates T-cell differentiation and immunomodulation – supported predominantly by animal and in vitro studies only [s1, s2].
Thymulin (formerly: Facteur Thymique Sérique, FTS) is a nonapeptide produced exclusively by thymic epithelial cells [s1]. It forms a biologically active complex with zinc; without zinc the peptide is inactive [s1, s2]. Thymulin was originally isolated from porcine serum and subsequently identified in calf thymus as well [s1]. The biological activity of thymulin declines with advancing age in parallel with thymic involution and correlates with decreasing plasma zinc levels [s3]. In the context of immunosenescence, thymulin is discussed as a potential candidate for restoring T-cell function in the elderly [s3, s4]. In the field of alopecia, preclinical and small clinical studies with topical zinc-thymulin (ZT) in androgenetic alopecia have been conducted, demonstrating moderate effects on hair growth [s5, s6]. For pain modulation and anti-inflammatory effects, only animal studies using a thymulin analogue (PAT) exist [s7, s8]. Clinical Phase 2/3 trials in humans for immunotherapy, cancer treatment, or autoimmune diseases using thymulin itself are absent [s9]. Development status at Santen Pharmaceutical was listed as "discontinued" [s10]. In the biohacking community, thymulin is occasionally confused with or equated to thymalin (a thymic polypeptide extract) – the two are biochemically distinct substances [s11].
Legal Status (DE)
Thymulin is not approved as a medicinal product in Germany, Austria, or Switzerland. No EMA or BfArM authorization exists for thymulin as a human medicinal product. The purchase and possession for research purposes is legally ambiguous; commercial dispensing as a medicinal product without authorization is prohibited under the German Medicinal Products Act (AMG). It is de facto traded as a research chemical. Use in humans outside of clinical trials is not regularly approved.
Mechanism of Action
Thymulin is a zinc-dependent nonapeptide secreted by thymic epithelial cells (TEC) [s1]. The zinc-thymulin complex binds to specific receptors on thymocytes and T-precursor cells, inducing their intra- and extrathymic differentiation into mature T-lymphocytes [s1, s2]. At the molecular level, thymulin modulates cytokine production: it inhibits pro-inflammatory cytokines (e.g., TNF-α) and regulates IL-2 [s12]. In animal models, a thymulin analogue (PAT) inhibited COX-2 and deactivated NF-κB, proposed as the mechanism underlying antihyperalgesic and anti-inflammatory effects [s7]. In pain models (rat), thymulin reduced thermal hyperalgesia and paw edema through modulation of spinal signaling pathways, including p38-MAPK inhibition and reduction of microglial activity [s8]. These findings derive exclusively from animal studies. In the context of alopecia, thymulin stimulates the anagen phase (growth phase) of hair follicles in vitro [s5]. Zinc, which is essential for activity, is itself involved in hair follicle proliferation [s5, s6]. The age-dependent decline in thymulin activity is attributed to falling plasma zinc levels; zinc supplementation can partially restore thymulin activity in elderly individuals [s3, s13].
Dosing
Systemische Immunmodulation (Forschungsprotokoll)
- Dose
- 2 mg subcutaneously daily
- Frequency
- 1× täglich abends
- Route
- injektion-subkutan
- Duration
- 20 aufeinanderfolgende Tage, 3× jährlich
- Timing
- Evening
- With food
- optional
Topische Anwendung bei androgenetischer Alopezie
- Dose
- Concentration corresponding to study preparation (ZT solution, exact concentration not published)
- Frequency
- Täglich topisch auf die Kopfhaut
- Route
- topisch
- Duration
- Studiendauer ca. 6 Monate
- Timing
- No specific time of day specified
- With food
- optional
No officially defined upper limit for humans. Animal studies showed no toxicity even at high doses [s13]. Due to the absence of human safety data, no reliable dosage recommendation can be made.
Thymulin requires zinc for biological activity; concurrent zinc supplementation (e.g., 15 mg/day) is recommended in protocols [s13, s11]. The dosages cited here originate from unregulated sources and clinical research protocols – none of which are officially approved for use in humans.
Calculate reconstitution, plan dosing, look up injection technique
Side Effects
| Side Effect | Frequency | Severity |
|---|---|---|
| Lokale Injektionsstellenreaktionen (Schmerz, Rötung) Occasionally described in reports on subcutaneous injection [s11, s14]. | gelegentlich | leicht |
| Müdigkeit Occasionally reported by users; no evidence from controlled studies [s11]. | selten | leicht |
| Kopfschmerzen Rarely described; no evidence from RCTs available [s11]. | selten | leicht |
| Gastrointestinale Beschwerden durch gleichzeitige Zink-Supplementierung Zinc >40 mg/day can cause nausea and GI complaints; well tolerated at zinc 15 mg/day [s13]. | gelegentlich | leicht |
| Kupfermangel bei chronisch hoher Zink-Supplementierung Long-term zinc >40 mg/day can cause copper malabsorption [s13]. | theoretisch | moderat |
| Immunstimulation mit möglicher Exazerbation von Autoimmunerkrankungen Thymulin stimulates T-cell differentiation; theoretical risk of exacerbating autoimmune processes cannot be excluded [s2, s9]. | theoretisch | schwer |
Contraindications
T-cell-stimulating properties may exacerbate autoimmune inflammation [s2, s9].
Immunomodulatory effects may promote graft rejection [s9].
Stimulation of T-cell proliferation in existing lymphatic malignancies is theoretically hazardous [s9].
No safety data available for pregnancy or lactation; use not recommended [s11].
No pediatric safety studies available; thymus remains functionally active in this age group [s4].
Interactions
Synergistic
Zinc is essential for the biological activity of thymulin; without zinc the peptide is inactive [s1, s2]. Co-administration (15 mg zinc/day) is recommended in protocols [s13].
Combined in community reports and longevity protocols; shared effects on immune aging mechanisms theoretically discussed; no controlled data [c3].
Caution
Antagonistic effect possible; thymulin may attenuate immunosuppression and compromise transplant rejection prophylaxis [s9].
Additive immunostimulation without controlled safety data; combination not recommended [s11, c1].
Community Evidence
Top reported benefits
- Subjectively perceived improvement in immune function (rarely reported)
- Less frequent colds (isolated reports, often referring to Thymalin)
- Combination effects with other peptides (purely anecdotal)
Top reported issues
- Confusion with Thymalin (frequently occurring in community discussions)
- Difficulty in procurement and quality control
- Barely reproducible personal anecdotal reports
The community data base is very thin; most threads in r/Peptides refer to thymalin (thymic polypeptide extract) rather than the specific nonapeptide thymulin [c1, c3]. Users predominantly discuss theoretical benefits based on mechanism articles. Reproducible self-reports with clear dosages and outcomes are absent. Concerns regarding product quality (research chemical market) are occasionally raised [c2]. Fewer than 30 usable individual user reports specific to thymulin are retrievable.
Scientific Sources
- Interactions between zinc and thymulin
Prasad AS, Bao B, Beck FW, et al. (2008). Journal of Trace Elements in Medicine and BiologyBPMID:18476235DOI - Thymulin drug profile – Synapse PatSnap
Synapse PatSnap Editorial (2024). synapse.patsnap.comCLink - Thymulin Dosing: 2mg/Day for 20 Days (2026)
The Peptide Catalog Editorial Team (2026). thepeptidecatalog.com (non-peer-reviewed)CLink - Thymulin – an overview (cytokine modulation)
ScienceDirect Topics Editorial (2023). ScienceDirect Topics – Immunology and MicrobiologyCLink - Thymulin: Research Evidence & Safety Profile
PeptideInsight Editorial (2024). peptideinsight.com (non-peer-reviewed)CLink - Thymalin – Wirkung, Anwendung & Risiken im Überblick
supplement-bewertung.com Editorial (2024). supplement-bewertung.com (nicht peer-reviewed)DLink - Thymic peptides and hormones: From their properties to clinical application
Goldstein AL, Goldstein A, Badamchian M, et al. (2024). International Journal of Peptide Research and TherapeuticsBDOI - Age-related thymic involution: Mechanistic insights and rejuvenating approaches to restore immune function
Dixit VD, Bhatt A, Dhru A, et al. (2025). Frontiers in ImmunologyBLink - The Effect of Age on Thymic Function
Hale JS, Boursalian TE, Turk GL, et al. (2013). Frontiers in ImmunologyBDOI - An Analysis of the Safety and Efficacy of Topical Zinc-Thymulin to treat Androgenetic Alopecia
Dreux AC, Bhatt D, et al. (2018). ResearchGate (conference proceedings / non-peer-reviewed)CLink - Zinc Thymulin – addressing hair loss (clinical overview)
Transform You Editorial (2023). transformyou.com (non-peer-reviewed)CLink - Potent analgesic and anti-inflammatory actions of a novel thymulin-related peptide in the rat
Saadé NE, Jabbur SJ, Safieh-Garabedian B, et al. (2006). British Journal of PharmacologyCLink - Thymulin treatment attenuates inflammatory pain by modulating spinal cellular and molecular signaling pathways
Neto JC, Borges BS, Ziviani L, et al. (2019). PubMed-indexed journalCPMID:30851702 - Thymulin: Benefits, Dosing & Where to Buy (2026)
The Peptide Catalog Editorial Team (2026). thepeptidecatalog.com (non-peer-reviewed)CLink
Community Sources
Storage
Unopened
Store frozen at -20 °C; lyophilized powder is stable for several years when stored properly.
Opened
After reconstitution with sterile water, store at 2–8 °C; use within 2–4 weeks.
Notes
Protection from light and heat required. No manufacturer specifications available, as no approved preparation exists; information is based on general peptide storage recommendations.