Mild induced testicular and epididymal hyperthermia alters sperm chromatin integrity in men.

Objective: To investigate the effects of a mild induced testicular and epididymal hyperthermia (+2°C) on sperm chromatin integrity in men.

Design: Experimental prospective study.

Setting: University hospital.

Patient(s): Five healthy fertile volunteers.

Intervention(s): Testicular and epididymal hyperthermia was induced by maintaining the testes at inguinal position with the support of specially designed underwear 15 ± 1 hours daily for 120 consecutive days.

Main Outcome Measure(s): Classic semen characteristics. Sperm DNA fragmentation index (DFI) and high DNA stainability (HDS) were analyzed by sperm chromatin structure assay.

Result(s): Compared with baseline values, sperm DFI and HDS were significantly increased as early as day (D) 20 and D34, respectively, and remained elevated during the entire period of hyperthermia. Percentages of motile and viable spermatozoa decreased as early as D20 and D34, respectively, and total sperm count decreased at D34 during hyperthermia and remained low during the entire hyperthermia period. All studied parameters returned to respective baseline values at D73 after cessation of hyperthermia.

Conclusion(s): Mild induced testicular and epididymal hyperthermia largely impaired sperm chromatin integrity, which appeared before any changes in sperm output. These findings may have clinical implications in male contraception, infertility, and assisted reproductive technology.