What the Numbers Mean: BPC-157, TB-500, GHRP-6

The numbers stuck to peptide names look like they should mean something exact: BPC-157, TB-500, GHRP-6, CJC-1295. It’s tempting to assume they’re doses, potencies, or amino-acid counts. Almost always, they’re not. Most are just identifiers — lab codes, catalog numbers, or a molecule’s place in a numbered series. A few are genuinely meaningful. The trick is telling them apart, so you never mistake a serial number for a strength. This is a short guide to answer the very common question why is it called BPC-157? — and what the other numbers are really doing. You can keep the definitions handy in our peptide research glossary.

The three kinds of numbers

Peptide-name numbers fall into three categories:

1. Lab or catalog codes — an arbitrary identifier assigned by the discoverer or manufacturer. Carries no chemical meaning. (Most numbers are this.)
2. Series positions — a molecule’s rank in a numbered family of related compounds.
3. True sequence coordinates — numbers that point to specific amino-acid positions in a protein. These are the informative ones, and they almost always appear as a range.

Most numbers in peptide names are lab or catalog codes — they identify the compound, not a dose, strength, or effect.

Sort any peptide’s number into one of these and you’ll know how much to read into it.

GHRP-6: a series number, not a size

The most common misconception is that the number counts amino acids. GHRP-6 is a hexapeptide — the 1984 Endocrinology paper that introduced it describes “a new synthetic hexapeptide” and gives the sequence as His-DTrp-Ala-Trp-DPhe-LysNH2, six residues — so the “6” looks like it must be the count. It isn’t. A 2026 structural study in Chirality tabulates the whole family side by side, and counting off its sequences settles it: GHRP-2 (D-Ala–Nal–Ala–Trp–D-Phe–Lys-NH2) is also six residues, while GHRP-1 (Ala–His–Nal–Ala–Trp–D-Phe–Lys-NH2) is seven. If the number were the amino-acid count, GHRP-1 couldn’t have seven.

The numbers in the GHRP (Growth Hormone-Releasing Peptide) family are series identifiers — they distinguish members of a related group of synthetic peptides developed over time. GHRP-6 being a six-residue peptide is a coincidence, not a rule. So the honest read of “GHRP-6” is: the sixth-labeled compound in the growth-hormone-releasing-peptide line, which happens to be a hexapeptide.

TB-500 and CJC-1295: catalog codes

TB-500. The “TB” is a clean abbreviation of Thymosin Beta. The “500,” however, has no explanation we could find in any peer-reviewed source. The molecule itself is a seven-amino-acid peptide, Ac-LKKTETQ, corresponding to residues 17–23 of thymosin β4 — and nothing about that maps to “500.” The most defensible interpretation is that 500 is a product or catalog code. Don’t infer a dose, a potency, or a fragment position from it.

CJC-1295. The 2005 Endocrinology paper that named the compound was written by researchers at ConjuChem Inc. in Montréal, and it describes CJC-1295 as the best of three candidate hGRF(1-29)–albumin conjugates the group synthesized and screened. That is what the number is: a company screening code for one molecule out of a series, not a chemical fact. (The chemistry that actually matters is hiding in a different number, discussed below.)

PT-141. Same pattern, and the regulatory record makes the point cleanly. PT-141 is now bremelanotide, FDA-approved as VYLEESI for hypoactive sexual desire disorder in premenopausal women. Its prescribing information gives a full structure — Ac-Nle-cyclo-(Asp-His-D-Phe-Arg-Trp-Lys-OH), molecular weight 1025.2 — and never mentions “PT-141” at all. The code was a development label; it carried no information the label needed to reproduce.

BPC-157: the debated one

Why is it called BPC-157? “BPC” stands for Body Protection Compound. The peptide is a pentadecapeptide — 15 amino acids, sequence Gly-Glu-Pro-Pro-Pro-Gly-Lys-Pro-Ala-Asp-Asp-Ala-Gly-Leu-Val, molecular weight 1419.55 daltons — and a 2025 review in Pharmaceuticals describes it as isolated from human gastric juice while sharing no sequence homology with known intestinal peptides.

The “157” is where the trail goes cold. It is usually described as a designation relative to the larger parent protein, but that review — which covers both the literature and the patent record — gives no explanation of what the number enumerates, and neither did any other peer-reviewed source we opened. Treat it as a research-group designation rather than a coordinate you can decode. What’s not in doubt: 157 is not a dose, not a potency, and not the number of amino acids (there are 15). For what the compound actually does — and doesn’t — see BPC-157: evidence vs hype.

The numbers that actually mean something

Contrast all of the above with numbers that genuinely encode chemistry. These almost always show up as a range in parentheses, pointing to amino-acid positions:

• GRF(1-29) — the first 29 amino acids of growth hormone-releasing factor. This is the backbone of CJC-1295 and sermorelin, and the “1-29” tells you exactly which stretch of the natural hormone was kept. It is specific enough that researchers infuse GHRH-(1-29)-NH2 into people and report its clearance as a distinct molecule.
• Thymosin β4 (17-23) — residues 17 through 23, the seven-residue stretch TB-500 reproduces.
• GLP-1(7-37) — the biologically active form of GLP-1, named for the residue positions that make up the mature hormone. The positions do real work here: in the 1987 study that identified it, GLP-1(7-37) stimulated insulin release from the perfused rat pancreas at concentrations as low as 5 × 10⁻¹¹ M, while GLP-1(1-37) — the same peptide with six extra residues on the front — had no effect even at ten thousand times that concentration.

When you see a hyphenated pair inside parentheses, that’s a real map of the molecule. When you see a single trailing number bolted to a name, assume it’s a code until proven otherwise.

Quick reference

Name	The number is…	Meaning
BPC-157	Research designation	No published explanation of what it enumerates; not a dose or residue count (it has 15 residues)
TB-500	Catalog/product code	No documented chemical meaning
GHRP-6	Series identifier	Member of the GHRP family; coincidentally a hexapeptide
GHRP-2	Series identifier	Different family member; also six residues
GHRP-1	Series identifier	Seven residues — the number and the count disagree outright
CJC-1295	Developer compound code	One candidate from a ConjuChem screening series
PT-141	Developer compound code	Absent from the drug’s own FDA label, which names only bremelanotide
GRF(1-29)	True sequence range	Amino acids 1 through 29 of the parent hormone
Thymosin β4 (17-23)	True sequence range	The seven-residue stretch TB-500 mimics

The honest caveat

Decoding a number is trivia, not a green light. A tidy identifier says nothing about whether a compound is effective, pure, safe, or legal — and most of these peptides are sold as research chemicals, not approved for human use, with limited or no controlled human data. TB-500 in particular is a short synthetic fragment with no completed human efficacy trials; we cover that evidence picture in TB-500: what the research does and doesn’t show.

So: read the number to identify the molecule, not to judge it. A range in parentheses is chemistry; a trailing number is usually a label. For the rest of the vocabulary, keep the peptide research glossary close. This is educational information about naming conventions, not medical advice — consult a qualified clinician before acting on any of it.

Sources

Sequences and residue counts come from the primary and peer-reviewed literature listed above, not from encyclopedia entries: GHRP-6 from Bowers et al. (1984), the rest of the GHRP series from the sequence table in Králík et al. (2026), BPC 157 from Józwiak et al. (2025), TB-500 from Mavrych et al. (2026), CJC-1295 from Jetté et al. (2005), GHRH-(1-29) from Soule et al. (1994), GLP-1(7-37) from Mojsov et al. (1987), and bremelanotide’s structure from its FDA prescribing information.

Two of this article’s claims are negative findings, and they are stated as such: the origin of TB-500’s “500” and the precise enumeration behind BPC-157’s “157” have no explanation in any source we opened. That is not the same as saying no explanation exists — only that we could not verify one, and neither should you trust a page that asserts one without a citation.