A 26-week randomized controlled trial found that growth hormone administration changed neither total nor free testosterone in older adults. The causal arrow that does exist runs the other way: testosterone modestly raises GH pulsatility and IGF-1, not the reverse.
No. Sermorelin does not raise testosterone, and this is not merely an evidence gap. A 26-week randomized placebo-controlled trial of growth hormone in adults aged 65 to 88 normalized IGF-1 but produced no significant change in total or free testosterone in either sex, and no change in luteinizing hormone secretion [1]. The GH axis and the gonadal axis are separate systems, and raising one does not pull the other up with it.
- A 26-week RCT found GH changed neither total nor free testosterone, nor LH [1]
- GH infusion in middle-aged men lowered SHBG but lowered total testosterone in parallel, leaving free testosterone unimproved [2]
- The canonical sermorelin trials either did not measure testosterone or measured it only at baseline [3][4]
- The real causal arrow runs the other way: testosterone modestly raises GH pulsatility and IGF-1 [5][6]
- Both can be low together because of a shared upstream pituitary cause, not because one drives the other [7]
What the Human Evidence Actually Shows
The most direct test available is a double-masked placebo-controlled trial of growth hormone in 48 adults aged 65 to 88, run for 26 weeks. GH normalized IGF-1, confirming the intervention worked. Total and free testosterone did not change significantly in either sex, and no luteinizing hormone secretory parameter changed [1].
That is a well-powered negative result on the exact question, using GH itself rather than a secretagogue. Since sermorelin works by stimulating the pituitary to release GH, and produces smaller pulsatile increases than administered GH does, it is not plausible that sermorelin achieves what GH administration did not.
A review of growth hormone effects on adult human gonads reaches the same place. It describes GH acting together with LH at the Leydig cell in animal work, but on human outcomes it is explicit that results are inconsistent and that testosterone levels in GH-deficient patients remained unaltered after GH treatment [8].
Where the Claim Comes From
A study where every patient was already on testosterone
The paper most often cited to support a testosterone benefit gave growth hormone secretagogues including sermorelin to 14 hypogonadal men, and testosterone rose substantially. Every patient in that study was concurrently on testosterone replacement therapy [9], and their LH and FSH were suppressed to 0.2 and 0.3 mIU/mL, which is the signature of exogenous testosterone rather than stimulated endogenous production. The testosterone rise is the TRT. The authors' own conclusion is confined to IGF-1, which rose from 159.5 to 239.0 ng/dL.
A libido finding in a trial that never measured testosterone
The 16-week trial of [[Nle27]GHRH(1-29)NH2, a norleucine-substituted analog of the fragment sermorelin is built on](https://pubmed.ncbi.nlm.nih.gov/9141536/) [3], reported improved libido in men on a self-administered questionnaire. That is a real finding and worth knowing. It is also frequently presented as evidence of a testosterone effect, which it cannot be: the hormone panel in that study covered GH, IGF-1, IGFBP-1, IGFBP-3, and GH binding protein. Testosterone was never drawn.
The earlier GHRH(1-29) trial in older men did measure testosterone, but only as a baseline age comparison, where it was lower in the older men [4]. No treatment effect on testosterone was reported.
Improved sleep, energy, and general well-being plausibly affect libido without any change in gonadal hormones. Attributing it to testosterone requires a measurement nobody took.
The SHBG Argument, and Why It Fails
A more sophisticated version of the claim holds that GH lowers sex hormone binding globulin, which would raise free testosterone even if total testosterone stayed flat. The direction is right and the conclusion still does not follow.
In middle-aged men given low-dose GH by continuous subcutaneous infusion for 14 days, SHBG fell, but total testosterone fell in parallel and the SHBG to testosterone ratio did not change [2]. Free testosterone was not improved. If anything, GH lowered testosterone in that study.
There is also a mechanistic wrinkle. When GH, IGF-1, and insulin were compared directly, SHBG tracked insulin, and no relation was found between IGF-1 and SHBG levels [10]. So the SHBG movement seen with GH is likely mediated through insulin rather than being an IGF-1 effect at all.
The Arrow Points the Other Way
There is a real interaction between these axes. It simply runs in the opposite direction from what the marketing claims.
In a randomized trial of men aged 65 and over with total testosterone below 350 ng/dL, transdermal testosterone raised GH pulse frequency relative to placebo and increased IGF-1 by 15.3 ng/mL [5]. The authors attribute the IGF-1 rise to aromatization of testosterone to estradiol. An earlier crossover study in normal men found that testosterone enanthate raised IGF-1 while nandrolone did not [6].
Two caveats keep this honest. The effect is modest, roughly 15 ng/mL of IGF-1. And it is not universal: in hypopituitary men already receiving GH, testosterone replacement left both total and free IGF-1 unchanged [11].
Why Both Are Often Low in the Same Patient
Men presenting with low IGF-1 frequently also have low testosterone, which is where the intuition that one drives the other comes from. The more likely explanation is a shared upstream cause. Pituitary damage can produce hypogonadotropic hypogonadism, growth hormone deficiency, central hypothyroidism, and central hypoadrenalism depending on which cell populations are affected [7].
Both axes decline with age independently as well. Two things falling on the same timeline is not evidence that treating one corrects the other.
If your testosterone is low, sermorelin is not the treatment for it. Have the gonadal axis evaluated on its own terms, including LH and FSH, rather than expecting a GH axis therapy to resolve it.
Combined Testosterone and GH Axis Protocols
Treating both axes when both are genuinely deficient is a different proposition, and the outcomes are additive rather than redundant. In a factorial randomized trial in older men over 16 weeks, lean mass rose 1.6 kg with testosterone alone and 3.0 kg with testosterone plus growth hormone, while strength rose 23% and 35% respectively [12].
Two qualifications matter before reading that as an endorsement. The trial used recombinant GH, not sermorelin, and no combined testosterone plus sermorelin outcome trial exists. And the combination carried a measurable cost: systolic blood pressure rose by 12 mmHg and hematocrit by 2.0% [12]. Combined protocols warrant monitoring rather than enthusiasm.
Sermorelin will not raise testosterone. If your goal is treating low T directly, PeterMD offers TRT with a physician evaluation and follow-up labs alongside its peptide programs.
Frequently Asked Questions
Does sermorelin increase testosterone?
No. A 26-week randomized placebo-controlled trial of growth hormone in adults aged 65 to 88 normalized IGF-1 but found no significant change in total or free testosterone, and no change in luteinizing hormone [1]. Sermorelin acts upstream of GH and produces smaller pulsatile increases, so it is not plausible that it achieves what GH administration did not. A review of GH effects on human gonads similarly reports that testosterone in GH-deficient patients remained unaltered after GH treatment [8].
Why do some clinics claim sermorelin raises testosterone?
Two sources of confusion. One study gave growth hormone secretagogues including sermorelin to hypogonadal men and reported a large testosterone rise, but every patient was concurrently on testosterone replacement therapy, and their LH and FSH were suppressed accordingly [9]. Separately, a GHRH analog trial reported improved libido in men [3], which is often presented as a testosterone effect even though that study never measured testosterone.
Does sermorelin increase free testosterone by lowering SHBG?
The evidence does not support this. In men given low-dose GH infusion for 14 days, SHBG did fall, but total testosterone fell in parallel and the SHBG to testosterone ratio was unchanged, so free testosterone was not improved [2]. A separate comparison found SHBG tracked insulin rather than IGF-1, with no relation between IGF-1 and SHBG [10], suggesting the SHBG effect is not an IGF-1 mechanism at all.
Does testosterone increase IGF-1?
Yes, modestly, and this is the direction with real support. In men aged 65 and over with low testosterone, transdermal testosterone raised GH pulse frequency and increased IGF-1 by about 15.3 ng/mL [5], with the authors attributing the effect to aromatization to estradiol. In normal men, testosterone enanthate raised IGF-1 while nandrolone did not [6]. The effect is not universal: in hypopituitary men already on GH, testosterone replacement did not change IGF-1 [11].
Can I take sermorelin and testosterone together?
When both axes are genuinely deficient, treating both produces additive results. A factorial trial in older men found lean mass rose 1.6 kg with testosterone alone versus 3.0 kg with testosterone plus growth hormone, and strength rose 23% versus 35% [12]. Two caveats: that trial used recombinant GH rather than sermorelin, and no combined testosterone plus sermorelin outcome trial exists. The combination also raised systolic blood pressure by 12 mmHg and hematocrit by 2.0% [12], so it requires monitoring.
My testosterone and IGF-1 are both low. Does one cause the other?
Usually not. A shared upstream cause is more likely, since pituitary damage can produce hypogonadotropic hypogonadism and growth hormone deficiency together, along with central hypothyroidism and hypoadrenalism, depending on which cells are affected [7]. Both axes also decline with age independently. Have the gonadal axis evaluated on its own terms with LH and FSH rather than expecting sermorelin to correct testosterone.
References
- Effects of growth hormone administration on luteinizing hormone secretion in healthy older men and women Physiological Reports, 2017. PMID: 29208686. https://pubmed.ncbi.nlm.nih.gov/29208686/
- Continuous subcutaneous infusion of low dose growth hormone decreases serum sex-hormone binding globulin and testosterone concentrations in moderately obese middle-aged men Clinical Endocrinology (Oxford), 1996. PMID: 8706289. https://pubmed.ncbi.nlm.nih.gov/8706289/
- Endocrine and metabolic effects of long-term administration of [Nle27]growth hormone-releasing hormone-(1-29)-NH2 in age-advanced men and women Journal of Clinical Endocrinology & Metabolism, 1997. PMID: 9141536. https://pubmed.ncbi.nlm.nih.gov/9141536/
- Growth hormone (GH)-releasing hormone-(1-29) twice daily reverses the decreased GH and insulin-like growth factor-I levels in old men Journal of Clinical Endocrinology & Metabolism, 1992. PMID: 1379256. https://pubmed.ncbi.nlm.nih.gov/1379256/
- Effects of transdermal testosterone gel or an aromatase inhibitor on serum concentration and pulsatility of growth hormone in older men with age-related low testosterone Metabolism, 2017. PMID: 28285644. https://pubmed.ncbi.nlm.nih.gov/28285644/
- Testosterone administration increases insulin-like growth factor-I levels in normal men Journal of Clinical Endocrinology & Metabolism, 1993. PMID: 7690364. https://pubmed.ncbi.nlm.nih.gov/7690364/
- Hypopituitarism The Lancet, 2024. PMID: 38735295. https://pubmed.ncbi.nlm.nih.gov/38735295/
- Effects of growth hormone on adult human gonads: action on reproduction and sexual function International Journal of Endocrinology, 2023. PMID: 37064267. https://pubmed.ncbi.nlm.nih.gov/37064267/
- Growth hormone secretagogue treatment in hypogonadal men raises serum insulin-like growth factor-1 levels American Journal of Men's Health, 2017. PMID: 28830317. https://pubmed.ncbi.nlm.nih.gov/28830317/
- Comparative effects of GH, IGF-I and insulin on serum sex hormone binding globulin Clinical Endocrinology (Oxford), 1994. PMID: 7923821. https://pubmed.ncbi.nlm.nih.gov/7923821/
- The growth hormone (GH)-insulin-like growth factor axis during testosterone replacement therapy in GH-treated hypopituitary males Growth Hormone & IGF Research, 2001. PMID: 11472076. https://pubmed.ncbi.nlm.nih.gov/11472076/
- Testosterone and growth hormone improve body composition and muscle performance in older men Journal of Clinical Endocrinology & Metabolism, 2009. PMID: 19293261. https://pubmed.ncbi.nlm.nih.gov/19293261/
