Sermorelin and Testosterone Interaction: What Patients and Clinicians Need to Know

What sermorelin is, and what it is not

Sermorelin acetate is a 29-amino-acid analogue of human growth hormone-releasing hormone (GHRH), the shortest synthetic peptide that keeps the full biological activity of GHRH [9]. It is not growth hormone. It acts on the pituitary's GHRH receptor and prompts the pituitary to release the body's own growth hormone. In healthy men given an intravenous dose, the peptide was eliminated quickly, yet growth hormone stayed elevated for about 3 hours [9][10].

Geref, the only FDA-approved sermorelin brand, had two approved uses: a diagnostic test of the pituitary's ability to secrete growth hormone, and treatment of idiopathic growth hormone deficiency in children with growth failure [3]. It was never approved for adults, anti-aging, weight loss or athletic performance [3]. The manufacturer discontinued it in 2008 and FDA withdrew both applications effective June 18, 2009 [3]. In 2013 FDA determined that Geref had not been withdrawn for reasons of safety or effectiveness [3].

Sermorelin sold in the US today is compounded, and compounded drugs are not FDA-approved. FDA does not review their safety, effectiveness or quality before they are marketed [6].

What the testosterone labels list as interactions

The Depo-Testosterone label's drug interaction section covers oral anticoagulants (increased sensitivity, possibly a lower anticoagulant dose, and more frequent INR and prothrombin time checks), oxyphenbutazone (higher serum levels), and diabetes medicines (lower blood glucose and insulin requirements) [1]. The enanthate label adds corticosteroids and ACTH, which together with testosterone may increase fluid retention [2]. The Depo-Testosterone label also warns that testosterone can increase blood pressure [1]. Sermorelin is not named in any of those sections.

Hematocrit: the best-documented overlap

Testosterone raises red blood cell mass, and how much depends on the formulation. A network meta-analysis of 29 randomized trials found that intramuscular testosterone enanthate or cypionate raised mean hematocrit by 4.0% versus placebo (95% CI 2.9 to 5.1); gel raised it 3.0% (95% CI 1.8 to 4.3) and patch 1.4% (95% CI 0.2 to 2.6) [4]. A retrospective review of 178 hypogonadal men followed for 3 years found erythrocytosis (hematocrit above 50%) in 66.7% of men on injectable testosterone, 35.1% on pellets and 12.8% on gels; the injection group was younger (mean 42.5 versus about 54 years) with a higher starting hematocrit, and this was not a randomized trial [11]. Another review reported a 315% greater risk of erythrocytosis (hematocrit above 0.52) in men on testosterone replacement than in controls [12].

The Depo-Testosterone label says to check hemoglobin and hematocrit periodically in long-term use [1]. The European Academy of Andrology guideline treats a hematocrit above 48% to 50% as a relative contraindication to testosterone therapy [13], and the Endocrine Society guideline recommends monitoring hematocrit during the first year [14].

On the sermorelin side, the 1-year pediatric trial of 110 children (86 evaluable) reported no adverse changes in general biochemical or hormonal tests, no change in fasting glucose, no excessive rise in IGF-I, and good overall tolerability [15].

Blood pressure

FDA's 2025 class-wide labeling action followed ambulatory blood pressure studies, which confirmed an increase in blood pressure with all testosterone products [5]. The Depo-Testosterone label says testosterone can increase blood pressure, which can increase cardiovascular risk over time, and that testosterone products are not recommended in men with uncontrolled hypertension [1].

Fertility

Testosterone inhibits pituitary luteinizing hormone and, at large doses, follicle stimulating hormone; the Depo-Testosterone label says this may suppress sperm production and possibly lower sperm count [1]. The Endocrine Society guideline recommends against starting testosterone in men planning fertility in the near term [14]. Recovery after stopping is common but variable: in one series of 66 men given high-dose hCG plus a selective estrogen receptor modulator after stopping testosterone, 46 (70%) reached a total motile count above 5 million within 12 months, and older age and longer prior testosterone use predicted slower recovery [16].

Sermorelin acts at the pituitary GHRH receptor [9], a different target from the LH and FSH suppression described on the testosterone label [1]. No study establishes what happens to fertility when the two are used together.

Glucose and fluid retention

The Depo-Testosterone label notes that androgens may lower blood glucose and insulin requirements [1]. Corticosteroids and ACTH used with testosterone may increase fluid retention, especially in people with heart, kidney or liver disease [2]. In the pediatric sermorelin trial, fasting glucose did not change over 12 months [15].

Dosing

No sermorelin dose is currently approved, because no sermorelin product is FDA-approved [3]. For context only, the pivotal pediatric program used 30 micrograms per kg subcutaneously once daily at bedtime [15], and a study of 10 healthy older men used 0.5 mg or 1 mg subcutaneously twice daily for 14 days [17]. Neither is a recommended dose today.

Testosterone dosing depends on the product. Depo-Testosterone is labeled at 50 to 400 mg every 2 to 4 weeks by deep gluteal intramuscular injection, after hypogonadism is confirmed with morning serum testosterone below the normal range on at least two separate days [1]. The intramuscular testosterone enanthate label gives the same 50 to 400 mg every 2 to 4 weeks range and says injections more often than every 2 weeks are rarely indicated [2].

Regulatory and sport status

Testosterone is a Schedule III controlled substance [18]. Both drugs sit on WADA's Prohibited List: sermorelin in S2.2.4 as a growth hormone releasing factor and testosterone in S1 as an anabolic agent, prohibited at all times, in and out of competition [7][8]. A prescription does not make either one permitted in WADA-governed sport; a Therapeutic Use Exemption is needed [8].