Pegvisomant
GH receptor antagonist
Also Somavert, B2036-PEG, Pegvisomant for injection
- Evidence
- AStrong human evidence
- FDA status
- FDA approvedas of 2026-10-26
- Route
- Injection
- Studies cited
- 1 human0 animal or cell
It is a daily injection for acromegaly, an illness where the body makes too much growth hormone. In a trial of 112 patients, the main blood marker returned to normal in about 89% at the top dose.
Sold for
Pegvisomant is the most effective drug for normalizing IGF-1 in acromegaly, and it is the reason bodybuilding forums sometimes discuss blocking growth hormone.
Studies say
A placebo-controlled trial normalized IGF-1 in nearly nine out of ten patients at the top trial dose, with symptom relief tracking the biochemistry, which is A-grade evidence for its approved use.
Why grade A. The trial was a randomized, double-blind, placebo-controlled study of 112 patients with acromegaly over 12 weeks, in which IGF-1 normalized in a large majority at the highest trial dose. The ACROSTUDY registry in the label followed 2,221 treated patients for a mean of 8.5 years for safety. The trial measured a biochemical endpoint, IGF-1, and not long-term outcomes, but IGF-1 is the accepted marker of disease activity. 12
FDA. Approved in 2003 as Somavert, a daily subcutaneous injection, for acromegaly in patients who have had an inadequate response to surgery or radiation therapy, or for whom those therapies are not appropriate. 2
Written from 2 cited sources. Fact-checked 2026-10-27: 14 claims checked, 3 corrected. Last refreshed 2026-10-27. Not physician reviewed.
What this means for you
- What people take it for
- Acromegaly (too much growth hormone)
- Can a US doctor prescribe it?
- Yes, FDA approved for acromegaly when surgery or radiation has not worked or is not suitable.
- Properly tested in people?
- Yes, in a controlled trial of 112 patients.
Evidence checklist
- Randomised controlled trial Double-blind placebo-controlled, 12 weeksyes
- Human study over 100 people 112 acromegaly patientsyes
- More than one research group Trial plus registry data from 20 yearsyes
- Clinical outcomes, not surrogate markers IGF-1 normalization, a biochemical markerno
- Human safety data beyond case reports Liver enzymes tracked; registriesyes
Drawn from the cited studies below. A dash means the sources give no information.
What it is
Pegvisomant is a modified version of human growth hormone that has been engineered to do the opposite of the natural hormone. Nine amino acid changes let it bind the growth hormone receptor without switching it on, and attached polyethylene glycol chains slow its clearance so one injection lasts a day. It is the only growth hormone receptor antagonist in clinical use. Pfizer sells it as Somavert. 12
Acromegaly is the disease of too much growth hormone, almost always from a pituitary tumor. In adults it enlarges hands, feet and facial bones, thickens skin and soft tissue, and raises the risk of diabetes, heart disease and early death. Pegvisomant is used when surgery and somatostatin analogs have not controlled it. 1
How it works
Growth hormone works by binding two receptor molecules at once and pulling them together, which starts the signal that tells the liver to make IGF-1. Pegvisomant binds one receptor site tightly and is altered at the second so the pair cannot form. The receptor is occupied but silent. Because the block is at the receptor, pegvisomant works regardless of how much growth hormone the tumor makes or which somatostatin receptors it carries, unlike octreotide and lanreotide, which act on the tumor itself. A consequence is that growth hormone levels in blood rise during treatment, so IGF-1 is the measure of control and growth hormone is not. 12
What human research shows
The trial randomized 112 patients with active acromegaly to placebo or one of three daily doses of pegvisomant for 12 weeks. IGF-1 fell in a dose-dependent way and reached the normal range in about 89 percent of patients at the highest trial dose, compared with about 10 percent on placebo. Soft-tissue swelling, excessive sweating and fatigue improved along with IGF-1, and ring size decreased. 1
The label summarizes ACROSTUDY, an observational registry of 2,221 patients treated for a mean of 8.5 years. Liver enzyme rises above five times the upper limit occurred in 1.7% of those with normal baseline tests, and on repeat MRI the pituitary tumor was reported larger in 7.1%, smaller in 17.3% and unchanged in 71.1%. 2
| Study | Model | Finding |
|---|---|---|
| Phase 3 (Trainer 2000) | Humans, n=112 with acromegaly, randomized double-blind placebo-controlled, 12 weeks | IGF-1 normalized in about 89 percent of patients at the highest trial dose versus 10 percent on placebo, with improvement in symptoms. 1 |
| Somavert prescribing information | FDA label | Documents the approved indication, liver monitoring, tumor imaging advice and injection-site warnings. 2 |
Safety
The main laboratory concern is the liver: elevations in transaminase enzymes occur in a minority of patients, usually reversible, and the label calls for liver tests before starting and at intervals afterward. Injection-site reactions are common; lipohypertrophy, a lump of fat tissue that forms with repeated injection in one place, is a listed warning but uncommon (1.6% in the registry). Other reported effects include infection, pain, nausea, diarrhea and flu-like symptoms. 12
Because pegvisomant does not shrink the pituitary tumor and may remove the feedback that restrains it, the label advises periodic imaging to check tumor size. Growth hormone blockade can lower blood sugar, so patients with diabetes may need less medication. 2
Questions for your clinician
- How is my tumor size monitored if pegvisomant does not shrink it?
- How often are my liver tests checked?
- How do I rotate injection sites to avoid lumps?
Questions people ask
Why do growth hormone levels go up on pegvisomant?
The drug blocks the receptor, not the tumor. With the receptor silenced, IGF-1 falls and the body loses the feedback that normally restrains growth hormone secretion, so blood levels of growth hormone rise even as the disease is controlled. Doctors follow IGF-1 instead. 12
Does it shrink the pituitary tumor?
No. Somatostatin analogs can shrink tumors modestly; pegvisomant does not act on the tumor at all. The label advises periodic MRI to check that the tumor is not growing. 2
Is pegvisomant used for anti-aging or to counter growth hormone abuse?
No. It is a prescription drug for a specific disease, and blocking growth hormone in a healthy person would be expected to cause the problems of growth hormone deficiency, not benefits. There are no trials of it outside acromegaly. 12
How does it compare with octreotide?
Octreotide suppresses growth hormone release from the tumor and works in roughly half of patients. Pegvisomant blocks the hormone's action and normalized IGF-1 in nearly nine in ten patients in its trial. Octreotide can shrink the tumor; pegvisomant cannot. They are often combined. 12
Citations
- Trainer 2000, N Engl J Med: treatment of acromegaly with the growth hormone receptor antagonist pegvisomant doi.org
- Pfizer: Somavert (pegvisomant) prescribing information labeling.pfizer.com