title: Seminal and molecular evidence that sauna exposure affects human spermatogenesis.
abstract: OBJECTIVE
  What are the effects of continuous sauna exposure on seminal parameters, sperm chromatin, sperm apoptosis and expression of genes involved in heat stress and hypoxia?
  
  
  CONCLUSIONS
  Scrotal hyperthermia by exposure to sauna can induce a significant alteration of spermatogenesis.
  
  
  BACKGROUND
  Several authors have evidenced that high temperature has dramatic effects on spermatogenesis.
  
  
  METHODS
  A longitudinal time-course study. Data from 10 subjects exposed to Finnish sauna were collected before sauna (T0), after 3 months of sauna sessions (T1) and after 3 (T2) and 6 months (T3) from the end of sauna exposure.
  
  
  METHODS
  Ten normozoospermic volunteers underwent two sauna sessions per week for 3 months, at 80-90°C, each lasting 15 min. Sex hormones, sperm parameters, sperm chromatin structure, sperm apoptosis and expression of genes involved in heat stress and hypoxia were evaluated at the start, at the end of sauna exposure and after 3 and 6 months from sauna discontinuation. Student's t-test for paired data was used for statistical analysis.
  
  
  RESULTS
  At the end of sauna exposure, we found a strong impairment of sperm count and motility (P < 0.001), while no significant change in sex hormones was present. Decreases in the percentage of sperm with normal histone-protamine substitution (78.7 ± 4.5 versus 69.0 ± 4.1), chromatin condensation (70.7 ± 4.7 versus 63.6 ± 3.3) and mitochondrial function (76.8 ± 4.9 versus 54.0 ± 6.1) were also evident at T1, and strong parallel up-regulation of genes involved in response to heat stress and hypoxia was found. All these effects were completely reversed at T3.
  
  
  CONCLUSIONS
  Absence of subjects with abnormal sperm parameters was the major limitation of this study.
  
  
  CONCLUSIONS
  Our data demonstrated for the first time that in normozoospermic subjects, sauna exposure induces a significant but reversible impairment of spermatogenesis, including alteration of sperm parameters, mitochondrial function and sperm DNA packaging. The large use of Finnish sauna in Nordic countries and its growing use in other parts of the world make it important to consider the impact of this lifestyle choice on men's fertility.
  
  
  BACKGROUND
  No external funding was sought for this study and the authors have no conflict of interest to declare.
authors: Department of Molecular Medicine, Section of Clinical Pathology and Pathology of Human Reproduction Unit, University of Padova, Via Gabelli 63, Padova 35121, Italy.
authors: Andrea
authors: A
authors: Garolla
authors: Mario
authors: M
authors: Torino
authors: Barbara
authors: B
authors: Sartini
authors: Ilaria
authors: I
authors: Cosci
authors: Cristina
authors: C
authors: Patassini
authors: Umberto
authors: U
authors: Carraro
authors: Carlo
authors: C
authors: Foresta
mesh_terms: D017209:Apoptosis; D015687:Cell Hypoxia / Q000235:genetics; D005640:Follicle Stimulating Hormone / Q000097:blood; D005786:Gene Expression Regulation; D018869:Heat-Shock Response / Q000235:genetics*; D006358:Hot Temperature; D006801:Humans; D007265:Inhibins / Q000097:blood; D008137:Longitudinal Studies; D007986:Luteinizing Hormone / Q000097:blood; D008297:Male; D012611:Scrotum / Q000166:cytology; D013076:Sperm Count; D013081:Sperm Motility; D013091:Spermatogenesis / Q000502:physiology*; D029002:Steam Bath; D013739:Testosterone / Q000097:blood
chemical_list: D013739:Testosterone; D007265:Inhibins; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone