Retatrutide and Testosterone: What Studies Report

Search interest in whether retatrutide "helps with testosterone" reflects a broader question in metabolic medicine: whether large reductions in body fat change androgen physiology. This page summarises what the published retatrutide literature reported, and — just as importantly — what it did not measure. This page is for educational purposes only and is not medical advice; consult a licensed physician about any medical or hormonal question.

The short answer from the literature

Across the verified retatrutide papers, no trial reported testosterone, luteinising hormone, follicle-stimulating hormone, sex hormone-binding globulin or any other gonadal endpoint. The phase 2 obesity trial measured body weight, waist circumference, glycaemic parameters, lipids and safety outcomes over 48 weeks (PMID 37366315). The phase 2 type 2 diabetes trial measured HbA1c and body weight across 36 weeks (PMID 37385280). Neither publication described sex-hormone assays. Any statement that retatrutide raises, lowers or preserves testosterone is therefore not supported by a measured trial result in this evidence base.

What retatrutide is, pharmacologically

Retatrutide (originally LY3437943) is a single peptide engineered to act as an agonist at three receptors: the glucose-dependent insulinotropic polypeptide (GIP) receptor, the glucagon-like peptide-1 (GLP-1) receptor and the glucagon receptor. The discovery and first-in-human work described this triple-receptor pharmacology and the initial clinical proof of concept (PMID 35985340). A phase 1b multiple-ascending-dose trial in people with type 2 diabetes then characterised safety, tolerability and early efficacy signals before the larger programmes began (PMID 36354040).

Reviews of the compound describe the three receptor arms as contributing complementary effects: GLP-1 receptor signalling linked to appetite suppression and slowed gastric motility, GIP receptor signalling linked to insulin secretion and adipose handling, and glucagon receptor signalling linked to energy expenditure and hepatic fat metabolism (PMID 40563436). A second review framed the same triple mechanism as the basis for the magnitude of weight change seen in trials (PMID 39515565). None of these receptor targets is a sex-steroid receptor, and the reviews did not describe direct gonadal or pituitary–gonadal actions.

Why the question arises: adiposity and androgen physiology

The interest in this combination is indirect. In endocrinology, excess adiposity and male hypogonadism are frequently discussed together, and weight-loss interventions are studied as a variable that may shift the hormonal picture. That literature is separate from the retatrutide trials themselves. What the retatrutide papers contribute is the first half of that chain — large, measurable reductions in fat mass — without the second half, because hormonal endpoints were not collected.

Magnitude of weight change reported

In the phase 2 obesity trial, researchers randomised adults with obesity to subcutaneous retatrutide at weekly doses of 1 mg, 4 mg, 8 mg or 12 mg, or placebo, and reported a mean weight reduction of 24.2% at 48 weeks in the 12 mg group compared with 2.1% with placebo (PMID 37366315). A Bayesian network meta-analysis comparing GLP-1 receptor agonists, dual agonists and retatrutide for weight loss in adults with overweight or obesity placed retatrutide at the top of the ranking for weight reduction among the agents analysed (PMID 40685589). A separate systematic review and meta-analysis of randomised trials reached a consistent conclusion on efficacy while flagging gastrointestinal tolerability as the dominant safety theme (PMID 40291085).

Body composition: the closest available proxy

The endpoint nearest to the testosterone question is body composition, because lean mass preservation is often raised in the same conversation. A substudy of the phase 2 type 2 diabetes trial examined body composition and reported that weight reduction with retatrutide comprised predominantly fat mass, with proportionally smaller reductions in lean mass (PMID 40609566). The study measured tissue compartments, not hormones; it did not report testosterone or any androgen marker, so it cannot be used to infer an endocrine mechanism behind the lean-mass findings.

Other metabolic endpoints studied

A randomised phase 2a trial in metabolic dysfunction-associated steatotic liver disease reported reductions in liver fat content with retatrutide over the treatment period (PMID 38858523). In type 2 diabetes, the phase 2 trial compared retatrutide with both placebo and an active comparator and reported dose-dependent reductions in HbA1c and body weight over 36 weeks (PMID 37385280). A phase 3 trial in people with type 2 diabetes inadequately controlled with diet and exercise extended these glycaemic and weight findings into a registrational setting (PMID 42250575). None of these publications listed sex-hormone outcomes.

Co-administration data with testosterone products

There are no published co-administration studies of retatrutide with testosterone esters, transdermal testosterone, selective androgen receptor modulators or human chorionic gonadotropin in the verified literature. The phase 2 and phase 3 publications described concomitant medication policies in terms of glucose-lowering and weight-related therapies, not androgen therapy, and no subgroup analysis by testosterone use was reported (PMID 37366315, PMID 42250575).

Pharmacologically, the two classes are dissimilar. Retatrutide is a peptide acting at three incretin-family and glucagon G-protein-coupled receptors (PMID 35985340), whereas testosterone products act at the nuclear androgen receptor after hepatic and tissue metabolism. That difference makes a shared-receptor interaction implausible on mechanism, but "implausible on mechanism" is not the same as "studied and found absent." The literature simply has not tested the pairing.

Adverse Events in Retatrutide Trials: What Studies Report

In the phase 2 obesity trial, researchers reported that the most common adverse events were gastrointestinal — nausea, diarrhoea, vomiting and constipation — that these were mostly mild to moderate, and that they were dose-related and partly mitigated by dose escalation (PMID 37366315). The same trial reported dose-dependent increases in heart rate during the treatment period. The phase 2 type 2 diabetes trial described a comparable gastrointestinal profile (PMID 37385280), and the earlier phase 1b multiple-ascending-dose study also identified gastrointestinal events as the principal tolerability limitation (PMID 36354040).

A systematic review and meta-analysis of randomised controlled trials pooled these safety data and reported a higher frequency of gastrointestinal adverse events with retatrutide than with placebo (PMID 40291085). No publication in this set reported endocrine adverse events involving the hypothalamic–pituitary–gonadal axis, sexual function or fertility. Absence of reporting is not the same as absence of effect; these outcomes were not systematically collected.

What ongoing programmes may or may not add

The TRIUMPH registrational programme was designed to evaluate retatrutide in obesity, obstructive sleep apnoea and knee osteoarthritis, and its published rationale and design paper set out the endpoint structure for those indications (PMID 41090431). Obstructive sleep apnoea is of tangential interest here because sleep-disordered breathing is discussed in the endocrine literature alongside androgen physiology, but the published design described respiratory, weight and joint endpoints rather than hormonal ones. Similarly, the phase 3 type 2 diabetes trial focused on glycaemic and weight outcomes (PMID 42250575). Based on the published designs, none of these programmes is positioned to answer a testosterone question directly.

How to read claims about retatrutide and testosterone

• Distinguish measured from inferred. Weight and body composition were measured (PMID 40609566); hormonal consequences were not.
• Check whether the source is a retatrutide trial at all. Many claims borrow from general obesity–hypogonadism literature and attach it to a specific compound.
• Note the population. The trials enrolled adults with obesity or type 2 diabetes (PMID 37366315, PMID 37385280), not men selected for low testosterone.
• Watch for extrapolation across drug classes. Findings from other incretin agents do not automatically transfer to a triple agonist with a glucagon receptor arm (PMID 39515565).
• Remember regulatory status. Retatrutide has been studied in registrational trials (PMID 41090431); material sold outside an approved pharmaceutical channel is not the same product studied in those trials.

Limits of this evidence base

The verified literature is weighted toward weight, glycaemia and hepatic fat, with trial durations reported at 36 weeks in type 2 diabetes and 48 weeks in obesity (PMID 37385280, PMID 37366315). Long-term endocrine follow-up, sex-hormone panels, fertility endpoints and interaction studies with androgen therapy are all absent. Readers evaluating claims in this area are looking at a genuine evidence gap rather than a contested finding. Questions about androgen status, hypogonadism or any hormone therapy belong with a licensed physician who can order and interpret appropriate testing.

References

• Triple-Hormone-Receptor Agonist Retatrutide for Obesity - A Phase 2 Trial (The New England Journal of Medicine, 2023)
• Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes: a randomised, double-blind, placebo and active-controlled, parallel-group, phase 2 trial conducted in the USA (Lancet, 2023)
• Effects of retatrutide on body composition in people with type 2 diabetes: a substudy of a phase 2, double-blind, parallel-group, placebo-controlled, randomised trial (The Lancet Diabetes & Endocrinology, 2025)
• LY3437943, a novel triple glucagon, GIP, and GLP-1 receptor agonist for glycemic control and weight loss: From discovery to clinical proof of concept (Cell Metabolism, 2022)
• LY3437943, a novel triple GIP, GLP-1, and glucagon receptor agonist in people with type 2 diabetes: a phase 1b, multicentre, double-blind, placebo-controlled, randomised, multiple-ascending dose trial (Lancet, 2022)
• Triple hormone receptor agonist retatrutide for metabolic dysfunction-associated steatotic liver disease: a randomized phase 2a trial (Nature Medicine, 2024)
• Efficacy and Safety of GLP-1 Receptor Agonists, Dual Agonists, and Retatrutide for Weight Loss in Adults With Overweight or Obesity: A Bayesian NMA (Obesity, 2025)
• Efficacy and safety of retatrutide, a novel GLP-1, GIP, and glucagon receptor agonist for obesity treatment: a systematic review and meta-analysis of randomized controlled trials (Proceedings (Baylor University Medical Center), 2025)
• Retatrutide-A Game Changer in Obesity Pharmacotherapy (Biomolecules, 2025)
• The power of three: Retatrutide's role in modern obesity and diabetes therapy (European Journal of Pharmacology, 2024)
• Retatrutide for the treatment of obesity, obstructive sleep apnea and knee osteoarthritis: Rationale and design of the TRIUMPH registrational clinical trials (Diabetes, Obesity & Metabolism, 2026)
• Efficacy and safety of retatrutide, a GIP, GLP-1, and glucagon receptor agonist, in people with type 2 diabetes and inadequate glycaemic control with diet and exercise (TRANSCEND-T2D-1): a double-blind, randomised, phase 3 trial (Lancet, 2026)