Considerations in evaluating human spermatogenesis on the basis of total sperm per ejaculate

Total number of sperm per ejaculate (TSperm) is an important measure for clinicians to provide advice to patient couples. However, TSperm per hour of abstinence (TSperm/h) is a better measure for epidemiologist-andrologist teams or clinicians to evaluate spermatogenesis because it is a rate function. This review looks at the interplay and impacts of rate of sperm accumulation in the excurrent duct system, abstinence interval, sexual arousal, and masturbation vs intercourse on observed TSperm. It also examines why and when TSperm/h might provide a meaningful quantitative evaluation of spermatogenesis (ie, rate of sperm production). There is no doubt that TSperm increases with longer abstinence, and in different men plateaus after 2-9 days. Clinicians wishing to maximize number of fully functional sperm available during intercourse, or for artificial insemination, might wish to recommend 6-7 days of abstinence. Diagnostically, the important feature is TSperm/h. After abstinence interval exceeds 64-72 hours, TSperm/h has started to decline in most nonoligozoospermic men as rate of sperm accumulation in the excurrent ducts approaches zero; apparently increasingly more sperm are voided in urine. Clinicians or epidemiologist-andrologist teams wishing to have optimal distinction among individuals with high, typical, or low sperm production (ie, normal or abnormal spermatogenesis) should accurately measure TSperm/h for samples provided after 42-54 hours' abstinence (never 64 hours). Longer abstinence intervals reward men with poor sperm production, because sperm accumulate in the excurrent ducts for 7 days or more of abstinence, and penalize men with good sperm production, because after 3 days or less of abstinence their excurrent ducts probably are full.