Follicle-stimulating hormone and human spermatogenesis

Area of Science:

• Reproductive Endocrinology
• Male Reproductive Physiology
• Spermatogenesis Research

Background:

• The precise role of follicle-stimulating hormone (FSH) in regulating human spermatogenesis remains incompletely understood.
• Previous studies have not definitively established the necessity of FSH for maintaining sperm production in men.

Purpose of the Study:

• To investigate the impact of experimentally induced, selective FSH deficiency on sperm production in healthy adult males.
• To determine if normal spermatogenesis can be sustained or reinitiated in the absence of significant FSH stimulation.

Main Methods:

• Five healthy men received weekly testosterone enanthate (T) injections to suppress luteinizing hormone (LH) and FSH, inducing azoospermia or severe oligospermia.
• Human chorionic gonadotropin (hCG) was administered concurrently with T to replace LH activity while maintaining FSH suppression.
• Sperm counts, motility, and morphology were assessed regularly throughout the study periods.

Main Results:

• Sperm counts significantly decreased during T administration alone (1.0+/-1.0 million/ml) compared to baseline (106+/-28 million/ml).
• Sperm counts recovered substantially with the addition of hCG to T (46+/-16 million/ml), returning to normal ranges in two subjects.
• Sperm motility and morphology remained normal throughout the hCG plus T treatment phase, despite undetectable serum FSH levels (<25 ng/ml) and suppressed urinary FSH excretion.

Conclusions:

• Spermatogenesis can be reinitiated and maintained at normal levels in men with undetectable blood FSH and very low urinary FSH excretion.
• These findings suggest that while FSH may influence testicular function, its near-complete absence does not preclude normal sperm production and quality in men.
• Normal spermatogenesis can occur despite minimal FSH stimulation, challenging the established view of its essential role.