Semaglutide, Low Testosterone, Nine Men

The whole study ran on nine men. Published in Scientific Reports on 23 June 2026, it examined DNA methylation and microRNA patterns in men treated with semaglutide for obesity-related low testosterone^[1]. Two of the nine were healthy controls. Seven had the condition the paper calls male obesity-associated secondary hypogonadism, or MOSH, meaning low testosterone driven by severe obesity rather than by a fault in the testes themselves. Four of those seven gave a second sample after semaglutide treatment^[2].

The authors call their own results "exploratory and hypothesis-generating", offering "preliminary observations to inform future validation studies"^[1].

What the study measured

Participants were men aged 20 to 40 with a BMI of 28 or above, using the obesity threshold applied to Chinese men, and total testosterone below 12 nmol^[2]. Men with uncontrolled diabetes, severe metabolic disorders or ongoing use of medication with known epigenetic effects were excluded^[2]. Blood and semen samples were collected between 8am and 10am^[2]. The methylation arm covered two controls, seven MOSH patients and four post-treatment samples. The microRNA sequencing covered two controls, seven patients and two post-treatment samples^[2].

Across that dataset the researchers reported 80 differentially methylated genes and six differentially expressed microRNAs^[1]. The largest number of those genes sat on the X chromosome^[2]. One microRNA, hsa-miR-423-5p, regulated most of them, and four proteins (DPP6, DPP10, CACNA1C and CNTNAP2) showed the strongest connectivity in the protein interaction network the authors built^[1]. Differential CpG methylation also turned up on chromosome 7, where the paper says the biological and functional relevance of the changes "remains unclear"^[2].

What a methylation association is, and what it is not

DNA methylation is a chemical tag that sits on DNA and changes how readily a gene gets read, without altering the underlying sequence. Methylation patterns shift with age, diet, illness, smoking and body weight. Finding that a set of genes carries different tags before and after a treatment tells you the pattern changed. It does not tell you the drug changed it, and it does not tell you the change did anything at all to the patient.

The authors state the same limitation directly. Their study, they write, is constrained by "the small sample size, the absence of an independent validation cohort, and the observational nature of the epigenetic analyses, all of which preclude causal inference"^[2].

Losing weight changes methylation on its own

No dataset this size can separate an effect of semaglutide from an effect of losing weight. Weight loss by itself rewrites blood methylation. A 2022 genome-wide analysis in Clinical Epigenetics, using blood from people with severe obesity (mean BMI around 45) who underwent bariatric surgery, found 41 significant and 1,169 suggestive differentially methylated positions associated with weight loss, along with 192 differentially methylated regions^[4]. Five of those CpG sites replicated in an independent cohort of BMI-discordant identical twins, and the surgery cohort showed decelerated epigenetic age at 12 months (mean change of -4.29, p = 0.02)^[4].

Semaglutide causes weight loss, so a methylation difference measured after semaglutide treatment could reflect the drug, the weight change the drug produced, or some mix of the two. This paper does not state the semaglutide dose or the treatment duration^[2], which leaves a reader unable to place the follow-up samples on any timeline, let alone apportion the signal.

The same ambiguity runs through the hormone side. A 2013 systematic review and meta-analysis in the European Journal of Endocrinology pooled 24 articles and found that both low-calorie dieting and bariatric surgery raised total testosterone in obese men, with surgery the more effective of the two, and that the degree of weight loss was the best single determinant of the rise^[3]. Low testosterone tied to obesity tends to improve when the obesity improves. Any treatment that produces weight loss inherits that effect.

Semaglutide is not approved for low testosterone

Semaglutide is a GLP-1 receptor agonist. Under the European marketing authorisation for Wegovy it is indicated for weight management in adults with a BMI of 30 or above, or a BMI of 27 to 30 alongside a weight-related condition such as prediabetes or type 2 diabetes, hypertension, dyslipidaemia, obstructive sleep apnoea or cardiovascular disease, and in adolescents from 12 years with obesity and body weight above 60 kg^[5]. Hypogonadism appears nowhere in that indication^[5]. A methylation paper in nine men does not move that line, and was never designed to.

What we don't yet know

Almost everything. Two controls give no usable comparison group, since one atypical individual moves the whole control average. Four paired samples cannot separate a treatment signal from noise. No validation cohort was run, and no functional experiment shows that any of the 80 genes behaves differently in living tissue. The enrichment on the X chromosome gets no explanation in the paper. Participants were young Chinese men above one specific BMI threshold, so nothing here generalises automatically to other populations. Blood methylation is also not testicular methylation, which leaves the link between the marks measured and the hormone problem being studied inferred rather than shown.

Why this matters

Studies this small are the raw material for bad headlines. A paper that honestly labels itself exploratory can arrive in a supplement newsletter as "semaglutide reprograms your genes", with the nine-person sample lost somewhere in the retelling. Credit belongs to these authors for saying outright that the chromosome 7 signal has no established meaning and that their analyses cannot establish cause and effect.

If you have both obesity and low testosterone, the useful next step is a conversation with an endocrinologist or your own prescribing clinician about both conditions together, not a search for an epigenetic mechanism. Our semaglutide regulation summary sets out where the drug is prescription-only, which is every country we track.

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