Is Testogel bioidentical? Yes, Testogel contains bioidentical testosterone that is molecularly identical to the hormone naturally produced by the male body. Licensed in the UK for treating male hypogonadism, Testogel delivers testosterone through a transdermal gel applied to the skin. Understanding whether testosterone therapy uses bioidentical hormones is important for men considering treatment options. This article explains what bioidentical testosterone means, how Testogel works, its benefits and risks, and who can safely use this licensed therapy under medical supervision in the UK.

What Is Testogel and How Does It Work?

Testogel is a transdermal testosterone replacement therapy (TRT) licensed in the UK for the treatment of male hypogonadism—a condition characterised by insufficient testosterone production. It is supplied as a clear, colourless hydroalcoholic gel containing testosterone as the active pharmaceutical ingredient.

The application method varies by formulation: Testogel 1% sachets can be applied to clean, dry, intact skin on the shoulders, upper arms, or abdomen, while Testogel 16.2 mg/g pump should only be applied to shoulders and upper arms. After application, the gel should be allowed to dry completely before dressing, and hands must be washed thoroughly. The application site should be covered with clothing once dry to prevent transfer to others. Patients should avoid showering or swimming for at least 2 hours (16.2 mg/g pump) or 6 hours (1% sachets) after application, and should wash the application site before any skin-to-skin contact with others. The gel should never be applied to the genital area and is flammable until dry.

Once absorbed, testosterone enters the bloodstream and binds to androgen receptors throughout the body, exerting its physiological effects. These include the maintenance of muscle mass and bone density, regulation of libido and sexual function, support of mood and cognitive performance, and stimulation of erythropoiesis (red blood cell production). Testogel is designed to restore serum testosterone levels to within the normal physiological range for adult males, with target levels guided by local laboratory reference ranges and symptom response, thereby alleviating symptoms associated with testosterone deficiency such as fatigue, reduced libido, erectile dysfunction, and loss of muscle strength.

The transdermal route offers several advantages including more stable serum testosterone levels compared to short-acting intramuscular injections, though long-acting injections can also provide stable levels. Careful application technique is essential to minimise the risk of transfer to others, particularly women and children.

Bioidentical vs Synthetic Testosterone: Key Differences

The term 'bioidentical' refers to hormones that are molecularly and structurally identical to those produced naturally by the human body. In the context of testosterone therapy, bioidentical testosterone has the exact same chemical structure (C₁₉H₂₈O₂) as endogenous testosterone synthesised by the testes. Testogel contains bioidentical testosterone, meaning the active ingredient is chemically indistinguishable from the hormone naturally produced in the male body. It's worth noting that all licensed testosterone products for male hypogonadism in the UK contain bioidentical testosterone.

This is an important distinction from synthetic testosterone derivatives or anabolic-androgenic steroids, which are structurally modified analogues designed to alter pharmacokinetic properties or enhance anabolic effects. Examples include methyltestosterone, nandrolone, and stanozolol. These synthetic compounds differ in their molecular structure and may exhibit different receptor binding profiles, metabolic pathways, and side effect profiles compared to bioidentical testosterone.

Bioidentical testosterone, as found in Testogel and other licensed TRT preparations, is metabolised by the body in the same manner as endogenous testosterone. It undergoes conversion to dihydrotestosterone (DHT) via 5α-reductase and to oestradiol via aromatase, maintaining normal physiological feedback mechanisms. This contrasts with some synthetic derivatives that resist enzymatic breakdown or exhibit altered androgenic-to-anabolic ratios.

In the UK, the Medicines and Healthcare products Regulatory Agency (MHRA) regulates all testosterone products, including Testogel, ensuring they meet stringent standards for quality, safety, and efficacy. The use of bioidentical testosterone in licensed formulations is supported by clinical evidence and is included in NICE Clinical Knowledge Summaries (CKS) and British Society for Sexual Medicine (BSSM) guidance for the treatment of confirmed hypogonadism. The choice of testosterone preparation should be based on patient factors and monitoring requirements rather than bioidentical status alone.

It's important to distinguish licensed products from unlicensed compounded 'bioidentical' hormones, which are not recommended by UK regulatory authorities.

Benefits and Risks of Testogel Treatment

Benefits of Testogel therapy in men with confirmed testosterone deficiency include:

• Sexual function: Enhanced libido, improved erectile function, and increased sexual satisfaction

• Body composition: Increased lean muscle mass, reduced fat mass, and improved strength

• Bone health: Increased bone mineral density, though fracture risk reduction has not been conclusively demonstrated

• Mood and cognition: Potential improvements in energy levels, mood, and quality of life, though effects vary between individuals

• Metabolic parameters: Some studies suggest benefits for insulin sensitivity and lipid profiles, but evidence remains mixed

The transdermal delivery system offers relatively stable testosterone levels throughout the day, avoiding the fluctuations associated with some short-acting injection regimens.

Risks and adverse effects must be carefully considered and monitored. Common side effects include:

• Skin reactions: Application site irritation, erythema, pruritus, or contact dermatitis

• Polycythaemia: Elevated haematocrit and haemoglobin, increasing thrombotic risk

• Prostate effects: Benign prostatic hyperplasia (BPH) symptom exacerbation; prostate-specific antigen (PSA) elevation

• Cardiovascular concerns: Potential increased risk of cardiovascular events, though evidence remains debated

• Transfer risk: Inadvertent exposure of partners or children to testosterone through skin contact

• Suppression of spermatogenesis: Reduced fertility during treatment

• Other androgenic effects: Acne, male pattern hair loss, gynaecomastia, and fluid retention

Monitoring should follow BSSM and NICE CKS guidance, including baseline assessment of full blood count (haematocrit), PSA (with digital rectal examination if indicated), and serum testosterone. Follow-up assessments should occur at 3, 6, and 12 months, then annually. Treatment should be adjusted or stopped if haematocrit exceeds 54%, and patients with concerning PSA changes should be referred to urology according to NICE NG12 criteria.

Patients should be counselled about the importance of adherence to application instructions and the need to report symptoms such as chest pain, leg swelling, breathing difficulties, or urinary symptoms promptly. Any suspected adverse reactions should be reported via the MHRA Yellow Card scheme. Testogel is contraindicated in men with prostate or breast cancer, and caution is advised in those with cardiovascular disease, sleep apnoea, or elevated haematocrit.

For a complete list of side effects, patients should consult the product's Summary of Product Characteristics (SmPC) or package leaflet.

Who Can Use Testogel in the UK?

Testogel is licensed in the UK specifically for adult males with hypogonadism confirmed by clinical symptoms and biochemical evidence of testosterone deficiency. Diagnosis requires the presence of characteristic symptoms—such as reduced libido, erectile dysfunction, fatigue, decreased muscle mass, or mood disturbance—alongside consistently low serum testosterone levels measured on at least two separate morning occasions. Results should be interpreted against local laboratory reference ranges, with additional measurements of luteinising hormone (LH), follicle-stimulating hormone (FSH), and sometimes sex hormone-binding globulin (SHBG) to help determine the cause.

The British Society for Sexual Medicine and European Association of Urology guidelines emphasise that testosterone therapy should only be initiated after thorough clinical assessment, exclusion of secondary causes of hypogonadism (such as pituitary disorders), and discussion of treatment goals and potential risks. Conditions that may benefit from TRT include:

• Primary hypogonadism: Testicular failure due to genetic conditions (e.g., Klinefelter syndrome), chemotherapy, radiation, or trauma

• Secondary hypogonadism: Hypothalamic-pituitary dysfunction, including age-related decline (late-onset hypogonadism)

• Chronic illness-associated hypogonadism: Conditions such as HIV, chronic kidney disease, or type 2 diabetes

Men planning to father children should be aware that TRT suppresses spermatogenesis and should be referred to endocrinology or andrology for alternative management options. Patients with suspected pituitary disease, markedly low testosterone with low/normal LH/FSH, or raised prolactin should be referred to endocrinology.

Testogel is not licensed for use in women or children in the UK. While testosterone therapy is sometimes used off-licence in women for specific indications (such as hypoactive sexual desire disorder in postmenopausal women), this requires specialist endocrinology or gynaecology input and careful dose titration with appropriate formulations.

Absolute contraindications include prostate cancer, male breast cancer, and hypersensitivity to testosterone or excipients. Relative contraindications requiring careful risk-benefit assessment include severe heart failure, untreated obstructive sleep apnoea, polycythaemia (haematocrit >54%), and severe lower urinary tract symptoms.

Patients considering Testogel should consult their GP or endocrinologist for comprehensive evaluation. Prescribing should occur within the NHS or through registered private providers, ensuring appropriate monitoring and follow-up. Patients should be advised to contact their healthcare provider if they experience chest pain, breathing difficulties, leg swelling, prolonged erections, mood changes, or urinary symptoms during treatment.

Frequently Asked Questions