Compared to the side effects of testosterone, the side effects of synthetic steroid hormones—especially 17-methylated steroids—are significantly more pronounced!
See the article on the side effects of anabolic steroids
The most significant side effect of testosterone is its androgenic effect. Especially when used illegally (doping in sports) in women, it leads to virilization (masculinization), acne vulgaris, androgenetic alopecia, hirsutism, and voice changes such as a hoarse or raspy voice (caution advised for women in singing or speaking professions!).
Prolonged use of testosterone leads to water retention and edema. Regarding its effect on the prostate in men, it should be noted that androgens such as testosterone can promote the growth of a malignant prostate tumor.
A summary of the numerous possible side effects from the 2014 Fachinformation, Testosterone Depot, Jenapharm®
| System organ class | Side effect |
| Benign and malignant neoplasms | Benign and malignant liver tumors |
| Disorders of the blood and lymphatic system | Polycythemia (erythrocytosis) |
| Immune system disorders | Hypersensitivity reactions |
| Liver and biliary tract disorders | Jaundice and abnormal liver function tests |
| Diseases of the skin and subcutaneous tissue | Various skin reactions (including acne, redness, hives, itching, and hair loss [alopecia]) |
| General_disorders_and_administration_site_conditions | Various_types_of_injection_site_reactions (injection site pain, injection site redness, injection site induration, injection site swelling, injection site inflammation) |
| Tests | Increase in prostate-specific antigen |
| Musculoskeletal system | Muscle cramps |
| Nervous system disorders and psychiatric disorders | Nervousness, aggression, depression, headaches, and fatigue |
| Respiratory, thoracic, and mediastinal dysfunction | Sleep apnea, upper respiratory tract infections |
| Gastrointestinal tract | Constipation, diarrhea, bloating, and abdominal pain |
| Diseases of the reproductive organs and the mammary glands | Changes in libido, increased frequency of erections; high-dose use of testosterone preparations generally causes a reversible interruption or reduction in spermatogenesis and, consequently, a decrease in testicular size; testosterone replacement therapy for hypogonadism can, in rare cases, cause painful prolonged erections (priapism), prostate abnormalities, prostate cancer*, and urinary retention. Chest pain, gynecomastia |
| Metabolic and nutritional disorders | Weight gain, changes in electrolyte levels (retention of sodium, chloride, potassium, calcium, and phosphate ions, as well as water) with high doses and/or long-term therapy |
* The data regarding the risk of developing prostate cancer in connection with testosterone treatment are unclear.
Literature: Fachinformation 2014, Testosterone Depot, Jenapharm®