Excessive heat may impact male fertility, Russian study finds

Researchers at the Institute of Immunology and Physiology, part of the Ural Branch of the Russian Academy of Sciences and Ural Federal University, have found that increased temperatures can disrupt the cellular balance necessary for normal male reproductive function.

While research into male infertility has traditionally focused on sperm—particularly their concentration, motility, function, and genetic characteristics—scientists are increasingly discovering that the microenvironment within the testes is equally important.

According to the Russian Science Portal, Boris Yushkov, head of the Laboratory of Immunophysiology and Immunopharmacology at the Institute of Immunology and Physiology, said that studies on male infertility have typically centered on sperm and their functional and genetic traits. However, growing evidence suggests that the microenvironment inside the testes plays a crucial role in ensuring proper sperm formation and natural testosterone production.

The researchers identified mast cells as one of the cell types that respond strongly to heat stress. Mast cells are immune cells containing biologically active substances that can affect neighboring cells when released. Under normal conditions, these cells participate in many regulatory processes, but heat may alter their behavior in ways that disrupt the reproductive environment's balance.

Ali Sadiq, a co-author of the study and a postgraduate student in the Department of Biology and Fundamental Medicine at the university, explained, "Our study shows that mast cells are among the cells that respond to heat stress. They contain various biologically active substances, and when activated, they release them, influencing surrounding cells."

Other daily factors may also contribute

The researchers note that changes in modern lifestyles may increase exposure to conditions associated with elevated local temperatures. Factors that may contribute to increased body temperature include a sedentary lifestyle, obesity, wearing tight underwear and trousers, and exposure to heat in the workplace. Temperature regulation is essential for normal sperm production, and the researchers emphasize that the biological consequences depend on the intensity and duration of heat exposure.

Yulia Khramtsova, a senior researcher at the Laboratory of Immunophysiology and Immunopharmacology at the institute, stated, "In many cases, these changes are reversible, and a single sauna visit is unlikely to cause permanent reproductive dysfunction in healthy individuals."

Khramtsova added that significant changes in sperm composition may occur in cases involving chronically elevated testicular temperature, such as undescended testes and varicocele, as well as in certain professions that require prolonged and regular heat exposure.