Cumulative Occupational Sunlight Exposure Associated with Oxidative Stress, Thyroid Hormone Alterations and Endocrine Dysregulation among Commercial Motorcycle Riders in a Tropical Setting

Abstract

Commercial motorcycle riders in tropical regions experience prolonged occupational exposure to intense sunlight and heat, which may influence oxidative and endocrine regulation. This study examined the association between cumulative occupational sunlight exposure and oxidative stress, thyroid hormone alterations, and endocrine dysregulation among commercial motorcycle riders in a tropical setting. A comparative cross-sectional design was used to evaluate 100 riders and 50 age-comparable controls. Oxidative stress markers (superoxide dismutase, catalase, malondialdehyde) and endocrine parameters (triiodothyronine, thyroxine, thyroid-stimulating hormone, luteinizing hormone, and prolactin) were measured using standard laboratory methods. Riders exhibited significantly reduced antioxidant enzyme activities and elevated lipid peroxidation compared with controls. Thyroid hormones T3 and T4 were significantly higher among riders, while thyroid-stimulating hormone showed no significant difference. Duration of riding demonstrated strong exposure-dependent associations with oxidative stress markers and thyroid hormone levels, alongside inverse relationships with pituitary hormones. These findings suggest that cumulative occupational sunlight exposure is associated with progressive oxidative stress and endocrine dysregulation, highlighting potential subclinical health risks among outdoor workers in tropical environments.