Progressive increases in the incidence of male reproductive disorders inclusive of hypospadias, cryptorchidism, poor semen quality, and testicular germ cell cancer (TGCC) have been observed in recent times. The central hypothesis of this study asserted that these disorders may all collectively signify testicular dysgenesis syndrome (TDS). This review aimed to provide evidence verifying the reality of TDS based on four key aspects: environmental endocrine-disrupting chemicals (EDCs), genetic factors, intrauterine growth disorders and lifestyle factors. Although TDS might result from genetic polymorphisms or aberration, recent evidence has highlighted links indicating the conditions associations to both environmental and lifestyle factors due to the rapid temporal changes in the clinical symptoms observed over recent decades. Based on our review of genetic and environmental factors, a key observation of our study suggested that there is an urgent need to prioritize research in reproductive physiology and pathophysiology, particularly in highly industrialized countries facing decreasing populations. At present, current research has yet to elucidate the mechanisms of TDS, in addition to the lack of genuine consideration of a variety of potentially key factors and TDS mechanisms. In conclusion, our study revealed that environmental exposures owing to modern lifestyles are primary factors involved in the associated trends of the syndrome, which are capable of affecting the adult endocrine system via direct means or through epigenetic mechanisms.Graphical abstract:
Testicular dysgenesis syndrome (TDS) development may be attributed to the following four key aspects: environmental exposure, genetic factors, intrauterine growth disorders, and lifestyle factors. These factors contribute to abnormal testis development in which disturbed Leydig cell differentiation and altered Sertoli cell differentiation are primary. Disturbed Leydig cell differentiation reduces insulin-like factor 3 (INSL3) and results in androgen insufficiency, and altered Sertoli cell differentiation leads to impaired germ cell function.