In March 2019 researchers from Australia published the results of their study to assess whether early signs of the metabolic disorder in late adolescence were associated with features of impaired testicular function. It is known that there has been a recent decline in sperm production which had been thought to be linked to environmental influences, but which many researchers now believe could be due to lifestyle factors in view of the simultaneous rise in obesity and diabetes type 2. A group of 17-year-old male adolescents underwent assessment with 490 being assessed for the presence of non-alcoholic fatty liver disease, 520 undergoing a serum cytokine assessment and 544 metabolic assessment. At age 20 years, 608 of the individuals underwent a further metabolic assessment, 609 an assessment of their reproductive hormones and 404 a testicular ultrasound, whilst 365 produced a semen sample. In addition, at both 17 and 20 years of age, fasting blood samples were also analysed. Results showed that those with an increased cardiometabolic risk at age 17 years had lower testosterone and inhibin B levels than those with a low cardiometabolic risk. Of particular note was that the presence of non-alcoholic fatty liver disease at 17 years of age, which was present in 10% of individuals, was associated with an almost 50% reduction in sperm output at 20 years of age, and that the presence of insulin resistance at 20 years was associated with a 20% reduction in testicular volume.
Hart RJ et al. Features of the metabolic syndrome in late adolescence are associated with impaired testicular function at 20 years of age. Hum Reprod. 2019 Mar 1;34(3):389-402.