Growth-hormone secretagogues

A growth-hormone secretagogue is anything that makes the pituitary release more of its own growth hormone. The ones sold for recovery are short injected peptides, and they come in two kinds. Sermorelin, tesamorelin and CJC-1295 are copies of growth-hormone-releasing hormone, the hypothalamic signal that tells the pituitary to secrete; ipamorelin, its older cousins GHRP-2, GHRP-6 and hexarelin, and the oral non-peptide MK-677 act instead on the ghrelin receptor, the second switch on the same cells. Either way the result is a rise in growth hormone and, downstream, in IGF-1, with the body's feedback loops still in place, which is the class's argument for being gentler than injecting growth hormone itself. Whatever the secretagogue, the molecule that reaches a joint is growth hormone or IGF-1, so this entry is about that axis as much as about the peptides. Its close relative AOD-9604, a fragment of growth hormone that does not raise IGF-1 at all, has its own entry.

Two routes to the same hormone

The releasing-hormone analogues differ mainly in how long they last. Sermorelin is the first 29 amino acids of the natural hormone. Tesamorelin is the full 44-residue sequence with a chemical group attached to slow its clearance. CJC-1295 carries four substitutions against enzymatic breakdown and is sold in two forms: with a drug-affinity complex, which binds albumin and keeps growth hormone elevated for days after a single injection, and without it, which is the version community protocols pair with ipamorelin on the theory that the pairing preserves the normal pulsatile rhythm. The ghrelin-receptor agonists are distinguished by their selectivity: ipamorelin releases growth hormone without the cortisol and prolactin surges the earlier releasing peptides produce, which is why it became the one people take.

What growth hormone does to a joint

The case for any of this in cartilage runs through IGF-1, which chondrocytes respond to by making matrix protein and by slowing the enzymes that degrade it; it can turn down MMP-3, a matrix-degrading enzyme, and turn up the enzyme that makes hyaluronan. The 2026 orthopaedic review of therapeutic peptides lists chondrocyte proliferation, matrix production and osteoblast differentiation among the effects of raised IGF-1, and says in the same paragraph that large-scale orthopaedic trials are lacking and the rationale rests on animal studies and indirect clinical evidence.

There is a second, older body of evidence about what this axis does to a joint, and it points the other way. Acromegaly, the disease of sustained growth-hormone excess, produces an arthropathy that virtually every patient develops: joint spaces widened by hypertrophied cartilage, osteophytes, symptoms in about seventy percent of patients even after their hormone levels are brought under control, and progression in a considerable proportion that continues independent of remission, with higher IGF-1 and longer exposure as the risk factors. The Leiden group that has studied it for two decades says the only treatment is normalising the hormone, that nothing tried for the joints themselves has been formally tested, and that joint replacement is the last resort. A joint bathed in too much growth hormone for too long is not a healthy joint, and any protocol that raises the hormone for years is running toward that literature rather than away from it.

The ghrelin receptor that ipamorelin acts on has been found on chondrocytes, and in one experiment on primary horse cartilage cells ghrelin protected them from an inflammatory injury at a high concentration while killing them at a low one, through a different receptor. That is the closest any published work comes to ipamorelin's target in a cartilage cell, and it was done with ghrelin itself.

Growth hormone itself, in a knee

The one randomised joint trial of the axis used recombinant growth hormone rather than a secretagogue. Nineteen men aged 18 to 35 having anterior cruciate ligament reconstruction at one centre injected either growth hormone or saline twice a day from a week before surgery to five weeks after. IGF-1 doubled over the treatment window. Six months after surgery the growth-hormone group's knee extension strength was 29 percent higher than placebo, the trial's primary outcome, with no difference at any earlier visit and no difference in quadriceps volume on MRI, which both groups lost about a fifth of in the first five weeks. A blood marker of cartilage breakdown, MMP-3, ran 36 percent lower on growth hormone. Patient-reported scores did not separate except one symptom subscale, which was consistently worse on the drug. The trial set its significance threshold at p < 0.10 because it was a pilot, was stopped by its safety committee on the strength result short of its planned size, and did not image cartilage; its authors call for a larger trial, and one is now registered. Thirty-four adults aged 18 to 60 with knee osteoarthritis who are not surgical candidates will inject the same dose once a day for six weeks alongside a strengthening programme, with strength at 12 weeks and radiographic progression at two years as secondary outcomes and a readout expected in 2028.

The human record, compound by compound

Tesamorelin is the one compound here with randomised trials inside an approved indication. The FDA approved it in 2010 for excess abdominal fat in people with HIV, where it cuts visceral fat by about 15 percent against placebo, and a weekly-reconstitution formulation followed in 2025. A secondary look at the two phase 3 trials, restricted to the 193 people who responded on fat against 148 on placebo, found trunk muscle density rising in every muscle group measured and lean muscle area rising with it; the density gain tracked the fat loss and the area gain tracked IGF-1, and neither trial measured strength or function. A 12-week trial in type 2 diabetes found no harm to glucose control. A trial as an adjunct to peripheral nerve repair is recruiting.

CJC-1295 with the drug-affinity complex has dose-escalation trials in healthy adults in which one injection raised growth hormone two- to tenfold for six days or more and IGF-1 up to threefold for nine to eleven days. The same trial recorded adverse events in 94 percent of participants on the drug against 29 percent on placebo, and a phase 2 trial in HIV lipodystrophy was halted after a patient died, with the cause debated; the registry lists it as terminated. CJC-1295 without the complex, the form in the popular stack, has no controlled human study of any kind.

Ipamorelin has a phase 1 study in healthy adults, well tolerated, with a growth-hormone peak at about an hour and no movement in other pituitary or adrenal hormones, and one randomised efficacy trial, in bowel-surgery patients with postoperative ileus, which found a week of the peptide safe and no better than placebo. No body-composition, performance or musculoskeletal endpoint has ever been measured in a person taking it.

Sermorelin was approved for children with growth-hormone deficiency and then discontinued by its manufacturer, with the FDA later ruling that the withdrawal was not for safety or effectiveness, which is the basis on which it is compounded today. The human evidence for a benefit in healthy adults is described by the most recent review as limited and largely indirect.

MK-677, or ibutamoren, is not in the orthopaedic reviews and is not a peptide, but it is the class's largest randomised test. Sixty-five healthy adults aged 60 to 81 took 25 mg a day or placebo for a year in an NIH-funded university trial. Growth hormone rose 1.8-fold and IGF-1 1.5-fold, into the young-adult range in about half. Fat-free mass rose 1.1 kg where placebo lost half a kilogram, and body weight rose 2.7 kg. Knee extension and flexion strength did not change, and no measure of function or quality of life moved. Fasting glucose rose, HbA1c rose, insulin sensitivity fell, cortisol rose, femoral-neck bone density fell slightly relative to placebo, and appetite increased in two-thirds. Joint pain was reported by more than half of both groups, and two women on the drug withdrew for it after a dose reduction. A second crossover year confirmed the first, and IGF-1 was back at baseline a month after stopping. A phase 2 trial in hip-fracture patients is listed as terminated.

The 2026 review that graded this literature put tesamorelin alone in its top tier, sermorelin, CJC-1295 with the complex and the ghrelin-receptor peptides in a middle tier of short studies with no body-composition or performance endpoint, and CJC-1295 without the complex at the bottom with no human study at all.

Dosing, regulation and safety

What the trials used: tesamorelin 2 mg a day under the skin; MK-677 25 mg a day by mouth, reduced to 10 mg in four people for rising glucose or joint pain; growth hormone at half a milligram per square metre of body surface twice a day for six weeks. The ipamorelin and CJC-1295 trial doses are in papers that could not be obtained for this entry. The community pairing of ipamorelin with CJC-1295 without the complex has, in the words of the review that looked for it, no controlled evidence of synergy, and the CJC-1295 actually sold is sometimes the long-acting form whose sustained stimulation the pairing is meant to avoid. This entry is an appraisal of published research, not dosing guidance.

Tesamorelin is approved for one indication in one country. Sermorelin is compounded on a withdrawn approval. CJC-1295 sits on the FDA's category 2 list of bulk substances for compounding, for reports of vasodilatory reactions and rapid heart rate. The class is prohibited by the World Anti-Doping Agency. What reaches most people who take these is compounded or gray-market product, with the purity, sterility and endotoxin problems the orthopaedic review sets out.

The trial safety record belongs to pharmaceutical product under monitoring. MK-677's year in older adults moved glucose, HbA1c, insulin sensitivity, cortisol and bone density in the wrong direction, produced appetite increase, oedema and muscle pain, and saw one tongue cancer and one heart attack on the drug in the first year. Growth hormone for six weeks in young men produced adverse events in eight of ten against seven of nine on placebo. Tesamorelin's side effects are mild to moderate: flushing, headache, dizziness, injection-site hives. Two concerns sit at the level of mechanism rather than of any trial: chronic ghrelin-receptor stimulation alters glucose handling, and the receptor is heavily expressed on the pituitary tumours that cause acromegaly.

What would move this

One study of any secretagogue with a cartilage endpoint would take this entry to preclinical whatever it found, because it would be the first. The growth-hormone knee-osteoarthritis pilot reporting in 2028 will be the first structural look at the axis in an arthritic human joint, and if it is positive the question of whether a secretagogue can do the same thing becomes a testable one. Short of that, the result this literature most needs is a trial of any of these compounds that measures strength or function rather than IGF-1, because the one year-long trial that did found the hormone rise and not the benefit.