Yes. But sperm count decline isn't one that I worry about," he added.
Obesity and Metabolic Health as Key Factors
Many endocrinologists agree that shifting societal metabolic health offers a more convincing explanation for documented hormonal shifts.
Prof Channa Jayasena, a consultant in reproductive endocrinology at Imperial College London, said, "There's been a profound shift in overall metabolic health."
Rising global rates of obesity and diabetes directly impact hormone production by accelerating the conversion of testosterone into estrogen.
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"Obesity could easily account for all of the decline," Jayasena explained. Increased body fat can elevate scrotal temperatures and disrupt brain signaling pathways essential for healthy sperm development.
Jayasena also warned against unregulated online sales of testosterone supplements, which can actively shut down natural sperm production.
"It's like a thermostat in a home – if you put a heater in the lounge it will switch off the boiler," he said.
Medical professionals warn against the growing trend of buying hormonal therapies without medical indications.
Meanwhile, rigorous laboratory evaluations indicate that some high-profile environmental contamination claims may rely on weak evidence.
Prof Rod Mitchell, a paediatric endocrinologist at the University of Edinburgh, noted that controlled experiments using human fetal testes tissue showed no developmental changes when exposed to common plasticizers like phthalates and BPA.
"They could just be sitting there inert and not doing anything," he said.
Mitchell dismissed extreme projections suggesting human sperm counts could drop to zero within the next few decades.
