Human mitochondrial DNA polymerase, encoded by POLG, contains a polyglutamine tract encoded by a CAG microsatellite repeat. Analysis of POLG genotypes in different populations identified an association between absence of the common, ten-repeat allele and male infertility typified by a range of sperm quality defects but excluding azoospermia.

Chronic inflammatory conditions of the genital tract are frequently encountered in male fertility problems. The diagnosis, however, is hampered by a mostly asymptomatic course of the disease as well as inappropriate definitions and unspecific diagnostic criteria. With regard to their impact on male reproductive function, epididymitis seems to be more relevant than inflammation/infection of the prostate and/or seminal vesicles. Chronic epididymitis may result in reduced sperm count and motility. Impaired sperm motility because of epididymal dysfunction is frequently associated with an atypical staining behaviour of sperm tails. In many cases of chronic epididymitis, the number of leukocytes in the ejaculate is below the threshold of 10(6) per ml; therefore, consideration of additional markers of inflammation such as granulocyte elastase, pro-inflammatory cytokines (e.g. interleukin-6 or 8) or reactive oxygen species is helpful for establishing the diagnosis. Besides changes in the conventional sperm parameters, alterations in DNA integrity have been observed. Positive effects of antiphlogistic/antibiotic treatment on semen quality have been reported; however, controlled prospective studies are still lacking.

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The effects of age on semen quality were analysed in patients referred to an andrology outpatient clinic in a retrospective study covering a period of 3 years. Semen analyses of older men (n = 66; > or = 50 years; median: 53) were compared with those of young patients (n = 134; 21-25 years; median 24). The duration of sexual abstinence was longer among older patients (median: 5.5 vs. 5.0 days; + 10%, P < 0.05). Even after adjustment for duration of sexual abstinence, progressive motility (- 27%, P < 0.01), percentage of morphologically normal spermatozoa (- 44%, P < 0.01) and semen volume (- 29%, P < 0.0005) were significantly lower in older than in younger men. Impaired sperm morphology was mainly attributed to abnormal staining of flagella (+ 50%, P < 0.05) and an increased portion of coiled or bent tails (+ 44%, P = 0.001) indicating epididymal dysfunction. Total sperm count and sperm concentration were unaffected by age. Age-dependent changes in accessory gland function, as indicated by fructose concentration (- 27%, P < 0.05), was correlated with lower semen volume. Moreover, serum testosterone levels were significantly reduced in the group of older men (median: 3.0 vs. 3.6 ng ml-1; -17%, P < 0.005).