Assessment of Testicular Function
An intact, functioning hypothalamic-pituitary-gonadal axis is also required for normal spermatogenesis and reproduction. FSH and LH support testicular Sertoli cell and Leydig cell function, respectively, and are responsible for testicular reproductive and androgenic function. Cancer treatment has been shown to potentially affect both aspects of testicular function in a dose-dependent and treatment-dependent manner.(67,75–77) Leydig cells (testosterone-producing cells) are generally more tolerant of chemotherapy and radiation, and androgen deficiency is much less common than impaired spermatogenesis in cancer survivors. As such, a normal testosterone level should not be interpreted as indicative of normal fertility. After high dose cranial radiation, high dose alkylating chemotherapy, or high dose testicular radiation, androgen deficiency can occur with specific symptomatology including loss of libido and with long-term health consequences, and will also negatively impact spermatogenesis.(30) Unfortunately, treatment of androgen deficiency with exogenous testosterone will impair spermatogenesis, and thus is not an appropriate treatment for men seeking fertility. Patients with hypogonadotropic hypogonadism following cranial radiation may have restored ability to sire children after treatment with gonadotropins.(78) It is for these reasons that early referral to urology or endocrinology is warranted.