Chapter 35 – Testicular Dysfunction

Publisher Summary The gonads have two distinct canonical functions—the production of functional gametes for fertilization and the secretion of gonadal steroids for sexual differentiation, maturation and near ubiquitous functional effects on organs and tissues. Consequently, gonadal dysfunction may be manifest as failure in either or both of its twin functions, such as infertility and/or steroid hormone deficiency. In men, testicular failure may become evident as isolated defects in spermatogenesis or steroidogenesis or both because the two axes operate in largely independent fashion with their inter-dependence only evident in extremes such as after orchidectomy or with complete gonadotropin deficiency. Most disorders of spermatogenesis—such as cytotoxic chemo- or radiotherapy effects on the testis or most causes of male infertility—however have essentially no, or at most, minimal clinical effects on androgen secretion or action. Conversely, acquired luteinizing hormone deficiency (LH) deficiency, such as with under-nutrition or other catabolic states that commence after completion of normal puberty and sperm production, may spare spermatogenesis. All known effects of the testis on bone are solely attributable to its gonadal steroid secretions and are unrelated to the testis's other function of spermatogenesis. Consequently, this chapter considers the effects of androgen (and/or estrogen) deficiency and avoids using the ambiguous term “hypogonadism” which is functionally non-specific and inaccurate.