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Thymulin

Last reviewed: April 18, 2026 by The Peptide Catalog Team

A thymic peptide for immune regulation and hair regrowth support. Thymulin (also known as Facteur Thymique Sérique or FTS) is a 9-amino acid peptide naturally produced by thymic epithelial cells. It requires zinc for biological activity and plays essential roles in T-cell differentiation, immune regulation, and neuroendocrine function. Research explores applications in immune aging, autoimmune conditions, hair loss, and as an anti-aging intervention. Thymulin levels decline significantly with age.

CategoryImmune & Thymic Peptides
Classimmune modulator
GoalImmune SupportSkin & Hair
Overview

Core Benefits

Key Advantages
Immune balance support
Supports T-cell maturation and immunosenescence.
Zinc-dependent activity
Requires zinc binding to activate — pair with zinc.
Anti-aging immune effect
Addresses age-related thymic decline.
Hair follicle research
Preliminary research on hair growth cycling.
HPA axis connection
Links to sleep, stress, and neuroendocrine balance.
Sparser community data
Endogenous peptide — drops 90%+ by age 60.

These are educational summaries of commonly discussed effects in wellness/regenerative contexts, not guarantees.

Thymulin Results Timeline

Progression
1
Week 1–2
Physical Changes
Subtle improvements in energy levels
Performance & Recovery
Immune system activation begins
Other Benefits
Ensure adequate zinc intake for activity
2
Week 3–6
Physical Changes
Possible hair/skin improvements, fewer infections
Performance & Recovery
Enhanced T-cell function
Other Benefits
Gradual immune marker improvements
3
Month 2–3
Physical Changes
Improved recovery, reduced inflammation
Performance & Recovery
Cumulative immune benefits
Other Benefits
May notice improved resilience, sleep quality
4
Long-term
Physical Changes
Anti-aging immune support
Performance & Recovery
Addresses age-related thymic decline
Other Benefits
Cycling recommended; pair with zinc supplementation

Timeline is illustrative and non-guaranteed. Outcomes vary and are commonly discussed alongside training, nutrition, sleep, and cycling practices.

Evidence at a glance

Two parallel grades per outcome — clinical RCT depth and real-world community adoption. See the Research Overview below for citations and detail.

OutcomeClinical EvidenceCommunity Evidence
Immune modulation (T-cell differentiation)ModerateWeak
Zinc-deficiency-related immune impairmentModerateWeak
Therapeutic use in healthy adultsPreliminaryWeak
How It WorksThymic Peptide — Zinc-Dependent Immune Modulator

Target → T-Cell Maturation → Immune Reconstitution → Outcomes

1
Target

T-Cell Precursors + Neuroendocrine Axis

Thymulin is a 9-amino-acid thymic peptide that requires zinc for biological activity. It promotes T-cell differentiation and maturation in the thymus and has neuroendocrine effects on the hypothalamic-pituitary axis. Thymulin levels decline dramatically with age as the thymus involutes.

2
Cellular Signal

T-Cell Maturation + Zinc-Dependent Signaling

Thymulin-zinc complex binds to T-cell precursors, promoting their differentiation into mature, functional T-cells. Also modulates cytokine production and has been shown to affect ACTH and beta-endorphin release. The zinc requirement means adequate zinc status is essential for activity.

3
Systemic Effect

Immune Reconstitution + Anti-Aging + Hair Growth

Enhanced T-cell function and immune competence. Neuroendocrine modulation may contribute to anti-aging effects. Research also shows potential for hair follicle stimulation — thymulin levels in hair follicles decline with age and may contribute to hair thinning.

4
What You Notice

Immune Support → Hair Improvements → Vitality

Improved immune function measurable via bloodwork over weeks. Potential hair growth improvements over months. Ensure adequate zinc supplementation for full biological activity. Effects are gradual and cumulative.

What Makes This Peptide Different

Thymulin is unique in its absolute zinc requirement — without zinc, it has no biological activity. This makes zinc supplementation essential when using thymulin. While Thymosin Alpha-1 is the more clinically validated thymic peptide, thymulin's additional research in hair growth and neuroendocrine modulation gives it a unique niche.

Research overview

Outcome-by-outcome look at what the evidence actually supports for Thymulin, including human vs. animal study counts and our editorial take on each.

Immune modulation

Clinical:ModerateCommunity:Weak

Bach and colleagues characterized thymulin (FTS-Zn) in the 1970s and 1980s as a zinc-dependent thymic hormone secreted by thymic epithelial cells that regulates T-cell differentiation and immune function. Thymulin activity declines with age and zinc deficiency. Most clinical literature is from the 1980s-1990s in malnourished or zinc-deficient populations — modern Western RCTs of synthetic thymulin in healthy adults are essentially absent.

1 human study · 12 animal studies

Key findings & citations
  • Bach 1989: thymulin's biological activity is zinc-dependent.
  • Prasad 1988: malnourished children show low thymic thymulin and zinc.
  • Thymulin levels correlate with circulating zinc and decline with age.
  • Modern human RCT data is essentially absent.

Our take

Real biology, dated literature, no modern controlled human trials. Community use is essentially nostalgic — most users would benefit more from confirmed adequate zinc intake.

What Thymulin doesn't do

Claims that current evidence does not support. Worth knowing before you set expectations.

Thymulin Vendors

15% OFF
COA
Limitless Biotech

Limitless Biotech

Score
10/10
Price
$16.99
$19.99
Amount
10mg
Cost/mg
$2.00/mg
Save 15% with code peptideinfo at checkout.
View at Limitless Biotech
Dosing ProtocolImmune Aging / T-cell Support

Educational reference only. Individual responses vary. Consult healthcare provider before use.

Vial Size
20 mg
Reconstitution
2 ml BAC water
Dose
2 mg (20 units on 1ml syringe)
Timing
PM
Frequency
Every day
Duration
20 days in a row, 3x per year
Protocol Notes
Requires zinc for biological activity — ensure adequate zinc status. 9-amino acid thymic peptide that declines with age. Short intensive cycles like Epitalon protocol.

Why This Dosing Protocol

Why ensure zinc status first? Thymulin without zinc is biologically inactive. Supplement with zinc (15-30mg/day) before and during thymulin use.

Why 5 on / 2 off? Standard cycling prevents immune over-stimulation while maintaining thymic peptide support.
Full Dosing GuideReconstitution CalculatorCycle Cost Calculator

Storage & Handling

Storage at a glance

Proper storage temperatures, shelf life, reconstitution best practices, and travel tips for lyophilized and reconstituted peptides.

Powder: Freezer
1+ year at -20°C
Reconstituted: Fridge
4 weeks max at 2-8°C
View Complete Storage Guide

Handling specifics

Educational overview on storage, labeling, and traceability considerations for lab environments. Consult primary literature and vendor documentation for specifics.

Powder storage (very stable)
  • Freezer (-20°C): 1+ year
  • Refrigerator (2-8°C): 1-3 months
  • Room temperature: 2-3 weeks (emergency only)
Reconstituted storage (fragile)
  • MUST refrigerate at 2-8°C
  • 4-week maximum shelf life
  • NEVER freeze after reconstitution
  • Use bacteriostatic water for multi-dose
Molecular Structure

Thymulin sequence

Click any residue to see its properties.

HydrophobicPolarAcidic (−)Basic (+)Special

Sequence-derived properties

Length
9 residues
Molecular weight
875.9 Da
backbone only
Avg hydrophobicity
-1.67
Kyte–Doolittle scale

Residue classes

Hydrophobic: 1 (11%)Polar: 5 (56%)Basic (+): 1 (11%)Special: 2 (22%)

Net charge distribution

Positive1 (11%)
Neutral8 (89%)
Negative0 (0%)

Amino acid frequency

G×2Q×2S×2A×1K×1N×1

Modifications

  • Requires bound Zn2+ for bioactivity

Sequence and properties provided for educational reference. Not for clinical dosing decisions.

  • Type: Thymic Peptide
    (9 amino acids)
  • Cofactor: Zinc Required
    (Zn-thymulin complex)
  • Target: T-lymphocytes
    (Differentiation)
  • Decline: ~90% by age 60
    (Thymic involution)
Mechanism
Thymulin + Zinc → T-cell receptor binding → T-cell differentiation → Immune maturation
Thymulin's requirement for zinc explains part of why zinc deficiency impairs immunity. Research focuses on immune aging, autoimmune conditions, and hair growth.
Key takeaway: As a key regulator of T-cell development that declines with age, thymulin is researched as a potential intervention for age-related immune decline.

FAQ

What is Thymulin?

Thymulin (also called Facteur Thymique Sérique or FTS) is a 9-amino acid peptide produced by thymic epithelial cells. It's unique because it requires zinc to be biologically active. Thymulin plays essential roles in T-cell differentiation, immune regulation, and has connections to neuroendocrine function. Its levels decline significantly with age.

Why does Thymulin require zinc?

Thymulin is only biologically active when bound to zinc — they form a zinc-thymulin complex. Without adequate zinc, thymulin cannot function properly. This is why zinc deficiency impairs immune function, and why thymulin supplementation should be paired with adequate zinc intake. The zinc-thymulin complex is what actually binds to T-cells.

How does Thymulin differ from Thymosin Alpha-1?

Both are thymic peptides but have different structures and mechanisms. Thymulin is 9 amino acids and requires zinc; Thymosin Alpha-1 is 28 amino acids and works independently. Thymulin focuses on T-cell differentiation and has neuroendocrine effects; Tα1 is more broadly immunomodulatory. Tα1 is approved as a drug (Zadaxin) while thymulin remains primarily a research peptide.

What is Thymulin used for?

Research focuses on immune aging (restoring declining thymic function), autoimmune conditions, hair loss (thymulin affects hair follicle cycling), and general immune support. Some anti-aging protocols include thymulin to address age-related immune decline. It's also studied for its neuroendocrine effects on sleep and stress responses.

Why do Thymulin levels decline with age?

The thymus gland shrinks (involutes) with age, dramatically reducing thymulin production. By age 60, thymulin levels may be 90% lower than in youth. This contributes to age-related immune decline (immunosenescence). Restoring thymulin levels is being researched as a way to partially reverse this immune aging.

What are the side effects of Thymulin?

Thymulin is generally well-tolerated as it's a naturally occurring peptide. Possible side effects include injection site reactions and rarely mild immune activation symptoms. Ensure adequate zinc status when using thymulin. Long-term safety data is limited as it's primarily used in research settings.

How long does reconstituted peptide last?

Once mixed with bacteriostatic water, peptides remain stable for up to 4 weeks when refrigerated at 2-8°C (36-46°F). Unopened powder can last 1+ year in the freezer. Get our complete Storage & Travel Guide.

Is this peptide legal to purchase?

Peptides sold "for research purposes only" are legal to purchase in the US, but are not FDA-approved for human use outside of specific medical applications. Always consult a healthcare provider before use.

New to peptides?

Take our Peptide Match tool to find the best peptide for your goals. You can also read our Complete Guide to Peptides to learn the basics.

Scientific Sources

The following peer-reviewed studies and official resources provide additional scientific context for this peptide:

Thymulin Research Articles

guides

Thymulin Dosage Chart: 2mg/Day for 20 Days

Thymulin is inactive without zinc — most protocols miss this. Covers 2mg SubQ PM dosing, zinc co-dosing, and 20-day cycling 3x/year.

results

Thymulin Results Timeline: What to Expect

Thymulin is an immune biomarker peptide, not a fast one. What research documents from week 1 to month 6 — and why most effects stay subclinical.

benefits

Thymulin Benefits: 7 Immune Effects

Drives CD4+ and CD8+ T-cell maturation and dampens TNF-α, IL-1β and IL-6. What the research shows as thymic output falls with age.

articles

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Disclosure: we may earn affiliate commission from qualifying purchases. Educational information only — not medical advice.