A male with azoospermia found to have normal FSH & testosterone levels & normal size testes. Probable cause is
High-Yield Explanation
Bilateral vas obstruction can cause azoospermia with normal FSH and testosterone levels and normal sized testis. Kallmann syndrome results from defective hypothalamic gonadotropin-releasing hormone (GnRH) synthesis. It is characterized by low luteinizing hormone (LH) and follicle-stimu- lating hormone (FSH) levels and low concentrations of sex steroids (testosterone or estradiol). Patients with undescended testis have different FSH and LH levels with the level of sperm density and spermatogenesis. The FSH levels in men are usually inversely correlated with sperm counts and indicate the integrity of seminiferous tubules, a marker of spermatogenesis. Patients with bilateral undescended testes have significantly lower sperm motility, sperm concentration, testicular volume and inhibin B levels, while showing higher FSH and LH levels than those with unilateral undescended testis. Klinefelter's Syndrome is characterized by small testes, infeility, gynecomastia, tall stature/increased leg length, and hypogonadism in phenotypic males.Plasma concentrations of FSH and luteinizing hormone (LH) are increased in most adults with 47,XXY, and plasma testosterone is decreased (50-75%), reflecting primary gonadal failure. Reference : page 2256 and 2350 Harrison's Principles of Internal Medicine 19th edition.