Sermorelin and gonadorelin: the older hormone-releasing peptides

Sermorelin and gonadorelin are copies of two of the brain’s own releasing hormones, and both were approved medicines in the US long before “peptides” became a wellness category. Sermorelin was approved for short children with growth hormone deficiency and withdrawn by its maker in 2008 for business reasons [2]. Gonadorelin was approved as a diagnostic test and as a pump therapy for infertility, and both US products are now discontinued [6,7]. The evidence for what they are marketed for today, anti-ageing and preserving fertility on testosterone, is much thinner than those histories suggest.

Two releasing hormones, two very different jobs

The hypothalamus controls the pituitary with short peptide signals. Two of them matter here:

The practical point is that both work only if the pituitary is there to respond. They do not replace a hormone; they ask the gland to make more of its own.

Sermorelin

What it was approved for

The FDA approved sermorelin as Geref in two forms: a small ampoule in December 1990 for testing whether the pituitary could release growth hormone, and larger vials in September 1997 for treating idiopathic growth hormone deficiency in children with growth failure [2].

A large published treatment study, from the Geref International Study Group, gave 110 previously untreated prepubertal children with growth hormone deficiency a nightly injection of 30 mcg/kg for up to a year [1]. It was open-label, with no placebo group. In the 86 children who could be analysed, average growth speed rose from 4.1 cm a year before treatment to 8.0 cm a year at six months and 7.2 cm a year at 12 months, and 74% were judged good responders at six months [1]. Bone age did not advance faster than height, and the authors reported no adverse changes in blood tests.

Why it disappeared

EMD Serono told the FDA in 2008 that it was stopping production, and the approvals were formally withdrawn from 18 June 2009 [2]. In 2013, responding to a citizen petition, the FDA published its determination that the Geref products “were not withdrawn from sale for reasons of safety or effectiveness” [2]. That is a narrow legal finding. It allows a generic application in principle, but it is not a fresh endorsement of the drug.

The adult and anti-ageing evidence

Sermorelin’s current appeal is as a gentler alternative to growth hormone for older adults. The trials behind that idea are small and short.

In 11 healthy men aged 64 to 76, nightly injections of 2 mg of GHRH(1-29) for six weeks increased night-time growth hormone release but did not raise IGF-1 [3]. Two of six strength measures and one endurance test improved; weight, body fat, muscle mass on DEXA and glucose tolerance did not change. There was no placebo group, and the authors concluded that a single nightly dose was less effective than multiple daily doses [3].

A second study used a closely related analogue, [Nle27]GHRH(1-29), in 19 adults aged 55 to 71: four weeks of placebo injections, then 16 weeks of the active drug, single-blind [4]. IGF-1 rose within two weeks but drifted back towards baseline by 16 weeks. Skin thickness increased in both sexes; lean body mass, insulin sensitivity, well-being and libido improved in men only. Transient raised blood fats were the only side effect reported [4]. This molecule differs from sermorelin by one amino acid, so it is supportive evidence at best.

That is a thin base for an anti-ageing claim: a few dozen people, a few months, hormone and body-composition markers rather than health outcomes, and in one study a waning IGF-1 response over time.

Gonadorelin

Why the pattern matters more than the dose

Gonadorelin’s story turns on a finding from rhesus monkeys in 1978. In animals whose own GnRH signal had been knocked out, a constant infusion of GnRH failed to restore LH and FSH release, while one pulse an hour, the natural rhythm, brought it back [5]. Switching from pulses to a continuous supply shut the system down again [5]. The lesson carried straight into medicine: gonadorelin used to restore fertility has to be given in pulses, usually by a small pump, because a steady supply switches the pituitary off rather than on.

What it was approved for

In the US, gonadorelin hydrochloride (Factrel) was approved in September 1982 as an injectable diagnostic, and gonadorelin acetate (Lutrepulse Kit) in October 1989 as an orphan drug for pulsatile therapy [6,7]. Drugs@FDA lists both as discontinued [6,7].

The fertility evidence

The strongest data come from people whose hypothalamus does not produce GnRH properly.

• Women with hypothalamic amenorrhoea: a 2018 meta-analysis pooled 35 studies (three randomised, 32 observational) covering 1,002 women [8]. Pulsatile GnRH produced high ovulation rates, the risk of ovarian hyperstimulation was low and mild, and multiple pregnancies were slightly more common than in the general population. Given under the skin, it worked about as well as by vein [8].
• Men with congenital hypogonadotropic hypogonadism: a 2021 meta-analysis of seven studies and 420 men compared pump GnRH with gonadotropin injections [9]. GnRH produced larger testes and sperm about five months sooner, but sperm detection rates, sperm counts and pregnancy rates were not significantly different. Allergic reactions were more common with GnRH [9].
• An Endocrine Society review describes fertility as inducible with either pulsatile GnRH or gonadotropins in most patients with this condition [10].

Gonadorelin alongside testosterone

The most common modern use is different: men on testosterone therapy injecting gonadorelin a few times a week, hoping to keep their testes working. That is not what the trials above tested. They used frequent pump pulses in men who had never made GnRH, not intermittent injections in men whose system is being suppressed by outside testosterone. A 2026 review of peptide strategies for testosterone-induced suppression concluded that direct evidence of restored sperm production or fertility “remains limited” [11]. We found no controlled trial of the typical injection schedule.

Status today

• US: neither drug has a currently marketed FDA-approved product. Sermorelin’s approvals were withdrawn for business reasons [2]; both gonadorelin products are discontinued [6,7].
• Sport: both are prohibited at all times under the 2026 WADA Prohibited List. Sermorelin is named under S2.2.4, growth hormone releasing factors; gonadorelin under S2.2.1, testosterone-stimulating peptides, which applies to male athletes [12].

What we still don’t know

• Whether sermorelin does anything for health, function or longevity in older adults over more than a few months.
• Whether IGF-1 responses to sermorelin fade with long-term use, as they did in one small study [4].
• Whether intermittent gonadorelin injections preserve fertility in men on testosterone.
• How compounded versions compare with the discontinued approved products for purity and dose.

Educational content only — not medical advice. Many peptides discussed on HPR are not approved for human use. Talk to a qualified clinician before making any decision about your health.

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