We always turn female issue when a couple is having trouble with fertility. We hardly discuss causes of male infertility. A new study in the Fall 2018 revealed that pre diabetes among men might be related to infertility.
Hormone levels as FSH, E2 and testosterone were studied in men with pre diabetes versus normal subjects. Those with pre diabetes had decreased levels of certain hormones.
After reading this study I believe like the authors that more studies need to be done. Pre diabetes in males can be a cause of male infertility when the female has no other problems to cause infertility