Spermatogenesis in man: an estimate of its duration.
Level 4 - case-series / case-control
Prospective physiological tracer study / case series without a control group
PubMed 13953583 · doi:10.1126/science.140.3563.184
What was done
Human testicular biopsies were obtained at various intervals following intratesticular injections of tritiated thymidine. Radioautographs were analyzed to track the progression of the most mature labeled germ cells over time.
What was found
The most mature labeled germ cells were preleptotene spermatocytes at 1 hour, midpachytene spermatocytes at 16 days, and immature spermatids at 32 days post-injection. Based on these observations, one cycle of the seminiferous epithelium was calculated to last 16 days, leading to an estimated duration of approximately 64 days for complete spermatogenesis.
Why it matters
This seminal study established the classic in vivo timeline of ~64 days for human spermatogenesis.
Limits
The abstract omits sample size, participant demographics, baseline fertility status, and variance estimates. Total time to ejaculation including epididymal transit was not assessed.
Cited by
- supports The human sperm turnover cycle is approximately 3 months.