What is Tesamorelin? A plain-English explainer
An FDA-approved, lab-made analog of growth-hormone-releasing hormone, marketed as Egrifta.
Tesamorelin is a synthetic peptide — a 44-amino-acid analog of growth-hormone-releasing hormone (GHRH) — approved by the FDA and marketed under the brand name Egrifta. A small chemical modification at one end of the molecule makes it more resistant to breakdown in the body than natural GHRH. It is a prescription-only medicine, not a research chemical.
That one paragraph is the whole definition. The rest of this page unpacks it at two levels — plain English, then a little deeper — and shows how the reconstitution math works, because the lyophilised form of tesamorelin has to be mixed and measured before it can be injected.
Tesamorelin in plain English
GHRH — growth-hormone-releasing hormone — is itself a 44-amino-acid peptide hormone, made naturally in the hypothalamus, that signals the pituitary gland to release growth hormone. Tesamorelin is a synthetic copy of that full 44-amino-acid sequence, with one added chemical group that helps it survive longer in the bloodstream than the natural hormone does.
Because it reproduces the entire GHRH sequence rather than a short piece of it, tesamorelin is often described as a “stabilised GHRH analog” rather than a fragment. So when you see the name, read it as: a lab-made, longer-lasting version of a hormone the body already makes, approved and prescribed for one specific medical use.
It is supplied as a lyophilised (freeze-dried) powder in a single-use vial, packaged with the diluent needed to reconstitute it, as part of an FDA-approved kit. On its own the powder can’t be measured into a syringe — there’s no volume to draw. That’s why the next step, reconstitution, exists.
The science, a little deeper
A few specifics that the plain-English version glosses over:
- It’s the full hormone sequence, not a fragment. Tesamorelin reproduces all 44 amino acids of GHRH, with a trans-3-hexenoic acid modification added to the front of the chain. That modification is what separates it, chemically, from unmodified natural GHRH, and is why it resists breakdown long enough to be given once daily.
- It’s supplied lyophilised. Removing the water gives the powder a long shelf life; adding back a precise, small volume of diluent (reconstitution) is what turns it into an injectable solution with a known strength.
- It carries full FDA approval — a fact, not a claim. Tesamorelin was approved by the FDA in 2010, initially under the brand name Egrifta and later in a reformulated version called Egrifta SV, for the reduction of excess visceral abdominal fat in adults with HIV-associated lipodystrophy. That is a narrow, specific approved indication — it is not a general approval for weight loss or for use outside that diagnosis.
If you want the classification in one line: tesamorelin is a synthetic, FDA-approved GHRH analog, 44 amino acids, supplied as a freeze-dried powder for reconstitution as part of a prescription kit.
How reconstitution works for Tesamorelin
Reconstitution is just dissolving the powder in a known volume of liquid so you have a concentration — milligrams of peptide per millilitre of solution. Once the concentration is fixed, the volume for any target dose is simple arithmetic:
- Concentration = vial amount (mg) ÷ diluent volume (mL)
- Draw volume = target dose ÷ concentration
- Syringe units = draw volume (mL) × the units-per-mL of your syringe
The numbers all come from your own vial label and your own prescription — the peptide amount printed on the vial, the volume of diluent specified in the kit, and the dose your prescriber specified. The separate Amidra web calculator runs exactly those three steps and shows the formula at each one, so you can check it by hand. It never fills in a dose for you.
What Amidra does — and doesn’t — do here
Amidra is a tracking and education tool. It converts the values you enter and helps you keep a protocol organised; it does not recommend a dose, a compound, or a schedule — even for an FDA-approved medicine like tesamorelin — and it takes no position on treatment decisions. Those decisions belong with a prescribing clinician. The information above is definitional — what the compound is and what it is approved for — not medical advice.