A young couple visits your rural general practice after trying to conceive for over a year without success. The woman’s fertility workup is completely normal. However, a semen analysis on the husband reveals azoospermia.
As his GP, you want to begin evaluating the possible cause. Which of the following is the most appropriate next step in his assessment?
A) Serum FSH level B) Serum LH level C) Serum testosterone level D) Anti-sperm antibodies
A) Serum FSH level
In the context of azoospermia (complete absence of sperm in the semen), the next logical step is to determine whether the cause is:
Obstructive azoospermia (normal sperm production but blocked ducts), or
Non-obstructive azoospermia (impaired or absent sperm production).
The serum FSH (follicle-stimulating hormone) level is the most important initial test to differentiate between these:
High FSH → Suggests primary testicular failure (non-obstructive azoospermia), as the pituitary increases FSH in response to low inhibin B from failing Sertoli cells.
Low or normal FSH → Suggests obstructive azoospermia or secondary hypogonadism.
Why other options are less appropriate as the next test:
B) Serum LH level – Useful in assessing Leydig cell function and testosterone regulation, but less specific for evaluating spermatogenesis directly.
C) Serum testosterone level – Assesses androgen status but doesn’t differentiate between obstructive and non-obstructive azoospermia.
D) Anti-sperm antibodies – Relevant in some cases of subfertility with sperm present; not useful in azoospermia.
