Tesamorelin, explained: asking the pituitary rather than replacing it

Tesamorelin is one of the few peptides in this catalogue whose design can be explained in a single sentence: it is the natural hormone with a cap on one end so the body cannot chop it up as fast. Everything else follows from that.

What it is

Growth hormone-releasing hormone, GHRH, is a 44-amino-acid peptide made in the hypothalamus. Its job is to travel a short distance to the anterior pituitary and tell it to release growth hormone. It is a messenger, not the message.

Tesamorelin is that same 44-residue sequence with a trans-3-hexenoyl group attached to the tyrosine at position 1. Its molecular mass is around 5,136 Da. The modification does one thing: it protects the N-terminus from dipeptidyl peptidase-4, the enzyme that clips native GHRH within minutes and is the reason the natural hormone is useless as a supplied compound.

This is the same problem the incretin analogues solve, and a useful illustration that peptide engineering is mostly a fight with a small number of enzymes. Tirzepatide blocks the same enzyme with a non-natural amino acid instead of an acyl cap.

Why an analogue rather than growth hormone itself

Growth hormone can be given directly, and is, as a licensed medicine. A GHRH analogue works a step upstream, and the difference is not cosmetic.

Released growth hormone is normally pulsatile. The pituitary puts it out in bursts, largest during slow-wave sleep, with quiet intervals between. Supplying growth hormone directly replaces that pattern with whatever curve the supplied material produces. A GHRH analogue asks the pituitary to release its own, so the pattern and the feedback loops that govern it, including inhibition by somatostatin and by circulating IGF-1, stay in place.

That is the theoretical case for the class. Whether it matters for any given research question is exactly the kind of thing the literature exists to answer.

How it differs from CJC-1295

Both are GHRH analogues and they are routinely confused. The short version:

The longer version, including what the DAC linker actually is, is here.

What has been studied

The compound was developed under the code TH9507 and has been studied most thoroughly in HIV-associated lipodystrophy, which is the indication it was licensed for in the United States. Falutz and colleagues reported the pivotal work in the New England Journal of Medicine in 2007. Non-clinical pharmacology and safety work was published the same year.

Outside that indication the literature is thinner, and we are not going to characterise it beyond saying so.

Regulatory status

Tesamorelin is approved in the United States under the brand name Egrifta for one narrow indication. It has no UK marketing authorisation, which means there is no licensed tesamorelin medicine in this country at all.

In the UK it may lawfully be bought, sold and held for laboratory research. It may not be sold or advertised for human or veterinary use. What that permission covers, and where sellers cross the line.

It sits on the WADA Prohibited List under the growth hormone secretagogue heading, and is prohibited at all times rather than in competition only. More on the list and what being on it means.

What matters for research supply

1. Identity. A 44-residue peptide with an acyl modification has a specific mass. The certificate should show it. How to read one.
2. Purity, method stated. What the figure means.
3. Quantity, separately from purity. Why both are needed.
4. Batch traceability through certificate, carton and batch lookup.
5. Storage — 2 to 8°C, dark, not frozen.

How Biovanta supplies it

Tesamorelin 32 mg is supplied in a factory-sealed pre-filled pen with sterile needles and prep swabs, manufactured in Switzerland and dispatched from the UK, with an independent Janoshik report per batch that you can verify by key on the testing page. Supplied strictly for in-vitro laboratory research.