The testis has an endocrine as well as an exocrine function. Endocrine testicular failure results in testosterone deficiency. In primary endocrine testicular failure, a decline in testosterone secretion (resulting in a condition termed hypoandrogenism) is caused by a deficiency or absence of Leydig cell function. Clinically relevant diseases described in this chapter are anorchia, Leydig cell hypoplasia and numerical chromosome abnormalities. Testicular dysgenesis is another cause for primary testicular failure that is described in depth in Endotext.com, Pediatric Endocrinology, Chapter 7: Sexual Differentiation. In contrast to primary endocrine testicular failure, secondary endocrine testicular failure is caused by absent or insufficient bioactivity of GnRH or LH (see Endotext.com, Endocrinology of Male Reproduction, Chapter 5: Hypogonadotropic hypogonadism and gonadotropin therapy).
The phenotype of primary exocrine testicular failure is male infertility. A comprehensive review on causes and treatment of male infertility is given in Endotext.com, Endocrinology of Male Reproduction, Chapter 7: Clinical management of male infertility. Cryptorchidism as a clinically relevant cause for primary exocrine testicular failure is discussed in Endotext.com, Endocrinology of Male Reproduction, Chapter 19: Cryptorchidism and hypospadias and testicular tumors as a cause and/or sequelae of testicular failure is discussed in Endotext.com, Endocrinology of Male Reproduction, Chapter 13: Testicular cancer pathogenesis, diagnosis and endocrine aspects.
This chapter focuses on anorchia, germ cell aplasia, spermatogenetic arrest, hypospermatogenesis, numerical chromosome abnormalities, structural chromosomal abnormalities, as well as Y chromosome microdeletions causing primary exocrine testicular failure.