The lower temperature in the scrotum is a prerequisite for normal spermatogenesis.
<Oxford Textbook of Medicine> by David A. Warrell, Timothy M. Cox, John D. Firth.page. 282, (line 32). Published by Oxford University.
- Heat can reduce sperm count and testosterone production.
University of Wisconsin Integrative Medicine
- According to this study from Nakamura et al. Human testis perform at their best when they’re around 31-36 °C (87-96 °F). anything hotter than that will negatively impact DNA synthesis, spermatogenesis, and most likely also testosterone production.
- A low testosterone [hypogonadism or testosterone deficiency syndrome (TDS)] may be present in 30% of men and present in a number of different ways.
European Heart Journal (OXFORD Academic)
The University of Edinburgh
- Low Testosterone Associated With Obesity and the Metabolic Syndrome Contributes to Sexual Dysfunction and Cardiovascular Disease Risk in Men With Type 2 Diabetes
American Diabetes Association
University of Buffalo