In recent years, there has been growing awareness that male reproductive
performance has declined. Numerous studies have focused on various aspects of
adverse trends in male reproductive health. There is a wealth of data that congenital
disorders, such as hypospadias, undescended testis, testicular atrophy and testicular
cancer have increased among young males. Testicular cancer, in particular germ cells
tumors, are the most common malignancy among young males accounting more than
10 cases per 100000 men per year in Europe. Both genetic predisposition and
environmental contaminants probably contribute for its etiology. Testicular germ cell
tumors arise from malignant transformation of testicular germ cells in a multistep
process where several aberrant modifications occur in genes involved in
proliferation/survival and differentiation. Individuals with testicular germ cell tumors
present a high survival rate but during treatments they are exposed to radio- and/or
chemotherapy that may induce permanent damages in male fertility. In this context, it
is essential to decipher the molecular mechanisms underlying testicular-related cancers.
However, other pathologies have also contributed to the decline of male reproductive
health, and particularly affect male sexual behavior. Inadequate penile erection,
commonly termed as erectile dysfunction (ED) mostly occurs in men older than 40
years. It is quite common in developed countries and compelling evidences have linked
the development of ED to diabetes mellitus, hypertension, hyperlipidemia, metabolic
syndrome and depression. In fact, it has been shown that certain environmental and
factors related to daily life, such as smoking, obesity, and limited or an absence of
physical exercise may also be key predictors of ED. Physicians have looked with
particular concern to these issues, but also for the sexually transmitted diseases (STDs).
Some STDs are resolved without treatment, but others have chronic lifelong infections.
In this chapter those topics will be discussed from a biochemical point of view and the
pathways that regulate the most relevant processes.
Keywords: Carcinoma in situ, Erectile dysfunction, Libido, Phosphodiesterase
inhibitors, Testicular cancer, Testicular germ cell tumors, Sexual behavior, Sexual
desire, Sexually transmitted diseases.
