VIP vs Thymulin
Comprehensive side-by-side comparison of mechanisms, dosing, side effects, and research
Also: Vasoactive Intestinal Peptide, Aviptadil
VIP (vasoactive intestinal peptide) is a 28-amino-acid signaling peptide your own gut, nerves, and immune cells make, first isolated in 1970 by Said and Mutt. It is a natural anti-inflammatory and a potent vasodilator, and a synthetic version called aviptadil was tested in humans for COVID-19 respiratory failure, where the largest trial was negative. No VIP product is FDA-approved, including for the wellness, anti-aging, or mold-illness uses it gets marketed for.
Also: Facteur thymique serique, FTS
Thymulin is a tiny nine-amino-acid hormone made by the epithelial cells of the thymus, first described in the 1970s as facteur thymique serique (FTS). It only works when bound to one zinc atom, which makes it an oddly neat marker of zinc status. It plays a part in training T cells, and animal work suggests anti-inflammatory and pain-reducing effects. It is sold online for immune support and hair loss, but there are no modern human trials of giving it, and the hair claims rest on lab dishes and a sponsor-linked cosmetic study.
Key Comparison Insights
- Both peptides belong to the Immune category, suggesting similar primary applications.
- VIP has stronger research evidence (Human Trials) compared to Thymulin (Preclinical).
Detailed Comparison
| Attribute | VIP | Thymulin |
|---|---|---|
| Category | Immune | Immune |
| FDA Status | Not FDA Approved | Not FDA Approved |
| Clinical Status | Pre I II III IV FDA | Pre I II III IV FDA |
| Mechanism of Action | VIP works through two G-protein-coupled receptors, VPAC1 and VPAC2, which are spread across immune cells, the gut, blood vessels, and the brain. When VIP binds, the receptor raises intracellular cyclic AMP, and that signal relaxes smooth muscle (so blood vessels and airways dilate) and tamps down inflammatory signaling. On the immune side, that rise in cAMP blunts NF-kB activity and lowers pro-inflammatory cytokines like TNF-alpha, which is the basis for calling VIP an endogenous anti-inflammatory. The same pathway is why researchers looked at it for the runaway lung inflammation seen in severe COVID-19. It is a broadly active hormone, not a targeted single-tissue drug, which is part of why dosing it safely is tricky. | Thymulin (sequence Glu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn) binds zinc in a 1:1 ratio, and only the zinc-bound form has biological activity. It promotes T cell differentiation inside and outside the thymus and influences T cell subsets and cytokine production. Its levels fall with age as the thymus shrinks, and fall with zinc deficiency. Researchers led by Goya and Reggiani have described a two-way link with the pituitary: thymulin seems to affect pituitary hormone release, and pituitary hormones affect thymulin secretion. In rodent models, thymulin and a synthetic analogue reduced inflammation and pain signalling, partly by dampening pro-inflammatory cytokines. How much of this applies to a peptide injected into a healthy adult is unknown. |
| Common Dosing | 50-100 mcg daily 1-2x daily | No established dose Unknown |
| Administration | IV infusion, inhaled, or intranasal | Sold for subcutaneous injection or topical use; neither route has been tested in controlled human trials |
| Typical Duration | Variable by indication | Unknown; no human trials to guide duration |
| Best Time to Take | Morning or as directed | No evidence-based timing |
Possible Side Effects May vary by individual |
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| Research Summary | Most of the real human data on VIP comes from aviptadil, the synthetic version (code RLF-100, brand Zyesami, developed by NRx Pharmaceuticals and Relief Therapeutics). A randomized trial of intravenous aviptadil in critically ill COVID-19 patients (about 196 patients, Critical Care Medicine 2022) missed its primary endpoint, with only exploratory signals. The bigger NIH ACTIV-3b/TESICO trial (Lancet Respiratory Medicine 2023, 461 patients) was clearly negative: no benefit on the 90-day recovery scale (odds ratio 1.11, p=0.54), 90-day deaths of 38% vs 36% on placebo, and it was stopped early for futility. The FDA declined emergency use authorization for COVID-19. Outside the US, aviptadil combined with phentolamine (Invicorp) is licensed as an injection for erectile dysfunction in the UK and some other European countries. VIP and its VPAC receptors are also studied in rheumatoid arthritis, pulmonary hypertension, and other inflammatory conditions, but that work is largely early-stage. There is no trial support for the anti-aging, wellness, or CIRS/mold claims VIP is sold for online. Bottom line: an interesting immune-modulating peptide, but its serious trials did not show it works. | Most of what is solid here is basic physiology. Dardenne and Pleau (1994) reviewed the zinc dependence: no zinc, no activity. Prasad and colleagues (JCI, 1988) showed that serum thymulin activity dropped in people made mildly zinc deficient by diet and came back with zinc supplementation, alongside shifts in T cell ratios and IL-2, so thymulin is a useful readout of zinc status. Reviews by Reggiani, Goya and colleagues (2012-2014) summarize anti-inflammatory and analgesic effects in rodents and gene therapy work in athymic mice, but frame human use as a future goal. On hair: Meier and colleagues (J Invest Dermatol, 2012) found a low dose of thymulin increased hair shaft growth in organ-cultured human scalp follicles, a dish result rather than a clinical one. A 2013 cosmetic study of a thymus peptide serum and shampoo reported less hair shedding on pull tests, but it was tied to the product maker and not a controlled regrowth trial. There are no controlled trials of injected or topical thymulin for immunity, aging or hair in people, and no human safety data. If you have low zinc, fixing that is better proven than adding the peptide. |
Frequently Asked Questions: VIP vs Thymulin
What is the difference between VIP and Thymulin?
VIP is a immune peptide that vip (vasoactive intestinal peptide) is a 28-amino-acid signaling peptide your own gut, nerves, and immune cells make, first isolated in 1970 by said and mutt. it is a natural anti-inflammatory and a potent vasodilator, and a synthetic version called aviptadil was tested in humans for covid-19 respiratory failure, where the largest trial was negative. no vip product is fda-approved, including for the wellness, anti-aging, or mold-illness uses it gets marketed for. Thymulin is a immune peptide that thymulin is a tiny nine-amino-acid hormone made by the epithelial cells of the thymus, first described in the 1970s as facteur thymique serique (fts). it only works when bound to one zinc atom, which makes it an oddly neat marker of zinc status. it plays a part in training t cells, and animal work suggests anti-inflammatory and pain-reducing effects. it is sold online for immune support and hair loss, but there are no modern human trials of giving it, and the hair claims rest on lab dishes and a sponsor-linked cosmetic study. The main differences lie in their mechanisms of action and clinical applications.
Which is better, VIP or Thymulin?
Neither is universally "better" - the choice depends on your specific goals. VIP is typically used for immune purposes, while Thymulin is used for immune. Always consult with a healthcare provider to determine which may be appropriate for your situation.
Can VIP and Thymulin be used together?
Some peptide protocols combine multiple compounds for synergistic effects. However, using VIP and Thymulin together should only be considered under medical supervision, as both compounds have their own side effect profiles and potential interactions. Research on their combined use may be limited.