Iodoacetic acid (IAA) is an emerging unregulated iodinated disinfection byproduct with high toxicity and widespread exposure. IAA has potential reproductive toxicity and could damage male reproduction. However, the underlying mechanisms and toxicological targets of IAA on male reproductive impairment are still unclear, and thus Sprague-Dawley rats and Leydig cells were used in this work to decode these pending concerns. Results showed that after IAA exposure, the histomorphology and ultrastructure of rat testes were abnormally changed, numbers of Leydig cells were reduced, the hypothalamic-pituitary-testis (HPT) axis was disordered, and testosterone biosynthesis was inhibited. Proteomics analyses displayed that oxidative stress, endoplasmic reticulum stress, and steroid hormone biosynthesis were involved in IAA-caused reproductive injury. Antioxidant enzymes were depleted, while levels of ROS, MDA, 8-OHdG, and γ-H2A.X were increased by IAA. IAA triggered oxidative stress and DNA damage, and then activated the GRP78/IRE1/XBP1s and cGAS/STING/NF-κB pathways in Leydig cells. The two signaling pathways constructed an interactive network by synergistically regulating the downstream transcription factor CHOP, which in turn directly bound to and negatively modulated steroidogenic StAR, finally refraining testosterone biosynthesis in Leydig cells. Collectively, IAA as a reproductive toxicant has anti-androgenic effects, and the GRP78/IRE1 and cGAS/STING pathway crosstalk through CHOP facilitates IAA-mediated testosterone decline.

As an emerging environmental endocrine disruptor, polystyrene microplastics (PS-MPs) are considered to have the anti-androgenic feature and impair male reproductive function. To explore the adverse effects of PS-MPs on testosterone synthesis and male reproduction and further elucidate underlying mechanisms, BALB/c mice and Leydig cells were employed in the present work. The results indicated that 50 μm PS-MPs accumulated in mouse testes and were internalized into the cytoplasm. This not only damaged the testicular histomorphology and ultrastructure, but also reduced the viability of Leydig cells and the serum level of GnRH, FSH, LH, and testosterone. After PS-MPs exposure, the ubiquitination degradation and miR-425-3p-targeted modulation synergistically contributed to the suppression of GPX1, which induced oxidative stress and subsequently activated the PERK-EIF2α-ATF4-CHOP pathway of endoplasmic reticulum (ER) stress. The transcription factor CHOP positively regulated the expression of SRD5A2 by directly binding to its promoter region, thereby accelerating testosterone metabolism and ultimately lowing testosterone levels. Besides, PS-MPs compromised testosterone homeostasis via interfering with the hypothalamic-pituitary-testis (HPT) axis. Taken together, PS-MPs possess an anti-androgenic characteristic and exert male reproductive damage effects. The antioxidant enzyme GPX1 plays a crucial role in the PS-MPs-mediated testosterone decline.

Previous cross-sectional and longitudinal studies have described decreasing testosterone levels with age in men, without consideration of acquired comorbidities in aging males.
We evaluated the longitudinal association between age and testosterone levels as well as the impact of several comorbidities on this relationship using multivariate panel regression analysis.
Participants were selected from the Baltimore Longitudinal Study of Aging. Data were obtained on the presence of several comorbidities and total testosterone level during each follow-up visit. A multivariate panel regression analysis was performed to determine the impact of age on testosterone level while controlling for individual comorbidities.
The primary outcomes were strength of association between age and various comorbidities, and testosterone level.
A total of 625 men were included in this study, with a mean age of 65 years and a mean testosterone level of 463 ng/dL. On multivariable-adjusted panel regression analysis, age was not significantly associated with testosterone decline, while anemia, diabetes mellitus, heart failure, obesity, peripheral artery disease, and stroke were inversely associated with total testosterone level. We report no association between cancer and total testosterone.
This study indicates that a decline in testosterone levels over time may be due to the presence of various comorbidities, which affects the medical management of hypogonadism in aging men.
The strengths of this study include the standardized acquisition of testosterone tests and uniform collection of variables, while limitations include the lack of follow-up data from 205 patients and the limited racial/ethnic diversity in the cohort.
In this large longitudinal study, we found that when adjusted for the presence of concomitant comorbidities, age does not predict a significant decline in testosterone level. With the overall increase in life expectancy and the simultaneous rise in the incidence of comorbidities such as diabetes and dyslipidemia, our findings may help optimize screening and treatment for late-onset hypogonadism in patients with multiple comorbidities.