Testosterone Replacement Therapy

Male hypogonadism (HG) can be defined according to its etiology as primary (pHG) when caused by any diseases affecting the testes, or as secondary (sHG) when due to a pituitary or hypothalamic dysfunction. Both fertility and testosterone (T) can be theoretically restored in sHG by removing the precipitating cause and/or by appropriate endocrine therapy. Conversely, only T treatment can be offered to patients with pHG. Symptoms and signs are quite similar independent of the underlying causes. Conversely, the phenotype of the hypogonadal patient is more often affected by the age of hypogonadism onset. Late-onset hypogonadism (LOH) that occurs in adulthood is probably the most common form of HG. In this chapter, the criteria defining LOH and the available T formulations along with their outcomes and main important side effects are analyzed in detail