Thymulin is a zinc-carrying thymus hormone that fades as the gland shrinks with age. Where zinc is low, the hormone is present but switched off, and restoring zinc switches it back on — the route with repeated human support. Injected thymulin rests on thin, decades-old evidence and has no approved source; the zinc doses used block copper absorption. (Full Review)
| Marker | Target | Why |
|---|---|---|
| Plasma zinc | 90–120 µg/dL | The cofactor that determines whether thymulin is active |
| Zinc-bound (active) thymulin | Detectable, within age-referenced range | The direct readout of the target being modified |
| Serum copper | 80–120 µg/dL | Detects the principal toxicity of the zinc route |
| Ceruloplasmin | 20–35 mg/dL | Confirms functional, not total, copper status |
| CBC with differential | Neutrophils 1.8–7.0 ×10⁹/L; haemoglobin mid-reference | Catches copper-deficiency anaemia and neutropenia early |
| CD4+/CD8+ T-cell ratio | 1.5–2.5 | Downstream marker of T-cell differentiation |
| hs-CRP | < 1.0 mg/L | Tracks the inflammatory load thymulin may lower |
| Interleukin-6 | < 2.0 pg/mL | Cytokine most tied to age-associated inflammation |
| TSH and free T4 | TSH 0.5–2.0 mIU/L; free T4 upper half of reference | Thyroid hormones drive thymulin output |
| Antinuclear antibodies | Negative | Screens for latent autoimmunity before immunomodulation |
| eGFR and serum creatinine | eGFR > 60 mL/min/1.73 m² | Governs peptide clearance and zinc handling |
Cadence: Baseline before dosing. Zinc, copper, ceruloplasmin, blood count at 6 and 12 weeks during zinc loading, then every 6 months. Active thymulin, CD4+/CD8+, hs-CRP, interleukin-6 at 12 weeks, then every 6–12 months. Thyroid and antinuclear antibodies at 6 months, or sooner if symptoms appear. Injection route: site and symptom check at 1 and 4 weeks.