Although diabetes is known to be associated with many complications, infertility amongst men is not traditionally thought of as being one of them.  Similarly, when a couple presents to a fertility clinic, diabetes in the man is not typically on the list of conditions to rule out.  As it turns out, diabetes in men can have an impact on fertility from several perspectives, right down to the DNA of the sperm themselves.
As reviewed by Sandro De Vignera and colleagues, the prevalence of subfertility or infertility amongst men with diabetes has been reported to be as high as 35-50% in some series, and is significantly higher than sub/infertility amongst men without diabetes.  Smoking and obesity appear to be the strongest risk factors for infertility amongst diabetic men.
There are several mechanisms by which diabetes can be associated with fertility problems.  It is well known that diabetes can be associated with erectile dysfunction, lower testosterone levels (particularly in cases of severe insulin resistance or obesity), and retrograde ejaculation (ejaculation ‘backwards’, into the bladder).
More recently, it has been discovered that diabetes can also be associated with damage to the DNA of sperm.  Studies suggest that diabetic men have a higher percentage of sperm with DNA damage compared to non diabetic men, and it has been postulated that this may be due to increased concentrations of ‘advanced glycation end products’ throughout the reproductive tract (proteins with sugar stuck to them, which is a consequence of elevated blood sugar over time), leading to more ‘stressed’ metabolic processes (known as ‘oxidative damage’) and thereby DNA damage.
While several of the above mentioned elements can occur in both type 1 and type 2 diabetes, there are some differences as well.  While type 2 diabetics are more likely to suffer from the insulin resistant mechanisms of infertility (obesity, low testosterone), men with type 1 diabetes have an increased risk of concomitant autoimmunity against the developing sperm or related structures.
While this topic can be discussed in far more detail than I have presented here, the key take home message today is that diabetes may play an important role in male factor infertility.  Fertility concerns or desires should be addressed in the evaluation of the diabetic male patient, and the possibility of diabetes should be considered in a man presenting with fertility concerns.
Dr Sue Pedersen © 2012 

Follow me on Twitter for daily tips! @drsuepedersen