A couple is evaluated for male infertility. Two semen analyses show azoospermia. Serum FSH is 2 mIU/mL (normal range 1.5 to 8) and testicular volume is normal bilaterally. What is the MOST likely diagnosis?

• A Non-obstructive azoospermia due to Sertoli cell only syndrome
• B Klinefelter syndrome (47,XXY)
• C Obstructive azoospermia ✓
• D Primary testicular failure following mumps orchitis

Explanation

Normal FSH with normal testicular volume indicates preserved spermatogenesis, pointing to obstruction such as congenital bilateral absence of the vas deferens or epididymal blockage. Non-obstructive azoospermia, Klinefelter syndrome, and post-orchitis failure all cause germ cell loss, which raises FSH through loss of inhibin C feedback and reduces testicular volume. Scrotal exploration or surgical sperm retrieval confirms the diagnosis.

Reference: Williams Gynecology, 4th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.