Testobase (Testosterone Suspension, typically 100 mg/ml in a 10 ml vial) is a fast-acting, water-based injectable form of pure, unesterified testosterone. Because it lacks an attached ester chain, it enters the bloodstream immediately upon intramuscular injection and has a very short half-life. Medical Uses Male Hypogonadism (Low Testosterone): It is used as hormone replacement therapy (HRT) for men whose bodies do not produce enough natural testosterone. It treats symptoms like severe fatigue, loss of muscle mass, decreased bone density, and low sex drive (libido). Delayed Male Puberty: It can be used under strict specialist supervision to induce secondary sexual characteristics (voice deepening, body hair, organ growth) in males experiencing significant developmental delays. Metastatic Breast Cancer Treatment: It is sometimes utilized as a secondary palliative treatment for specific types of advanced, hormone-responsive breast cancer in women.