Which finding would most strongly suggest non-obstructive azoospermia on initial male evaluation?

• A. Normal testicular size with normal or near-normal FSH.
• B. Normal testicular size with elevated FSH.
• C. Small/firm testes with elevated FSH.
• D. Large testes with low FSH.

Answer: (C)

Non-obstructive azoospermia arises from impaired sperm production within the testes. When the seminiferous tubules are damaged, inhibin B falls and FSH rises as the pituitary tries to stimulate the testes. The combination of small, firm testes with an elevated FSH reflects intrinsic testicular failure and reduced spermatogenesis, which is the strongest clue pointing to NOA on initial evaluation. In contrast, obstructive azoospermia preserves testicular function, so testicular size is typically normal and FSH is not elevated. The other patterns are less consistent with NOA because they do not pair signs of intrinsic testicular failure with abnormal gonadotropin feedback.