INS and diabetes mellitus: The following keywords were searched: ‘Hyperglycemia’ OR ‘Blood Glucose’ OR ‘Insulin’ OR ‘Male Infertility’ OR ‘Testis’ OR ‘Spermatogenesis’ OR ‘Sperm’ OR ‘Semen’ OR ‘DNA’ OR “diabetes” OR “spermatogenesis” OR “methylation” OR “DNA fragmentation” OR “histones” in combination with other search phrases relevant to the topic of hyperglycemia used.