The function of the male gonad, the testis, is devoted to androgens and spermatozoa production and is tightly regulated by the action of two pituitary gonadotropins (Gn): follicle-stimulating hormone (FSH) and luteinizing hormone (LH). In turn, the medial preoptic area (MPA) of the hypothalamus regulates Gn secretion through Gn releasing hormone (GnRH), which is controlled by a complex array of neurotransmitters, the most important represented by kisspeptin. Male hypogonadism is a pathological condition resulting from impairment in hypothalamus-pituitary-testis (HPT) axis activity due to a large variety of diseases, which leads to a defective production of testosterone and sperms [1, 2∗, 3].

Male hypogonadism (HG) is frequent, in particular in the aging male. In fact, male HG affects - in its symptomatic form - more than 2% of the European general population older than 40 years [4]. In middle-aged and elderly men, the most specific symptoms of T deficiency pertain to sexual dysfunction and include loss of sexual desire and reduced spontaneous or sex-related erections [4, 5, 6, 7]. Other common signs and symptoms are infertility, osteoporosis, fatigue, altered body composition (i.e. increased fat and decreased lean mass), and psychological disturbances [8, 9, 10, 11, 12]. Pharmacotherapy of male hypogonadism is essentially dictated by several factors, including the etiology of hypogonadism, the age of onset of the deficiency, its possible reversibility and last, but not least, the patient's needs [1, 2∗, 3,13,14].