The present study evaluated the ameliorative effect of vitamin C on alteration in thyroid hormones induced by low-dose subchronic coadministration of chlorpyrifos (CPF) and lead (Pb). Forty Wistar rats were divided into 4 groups of 10 animals each. Groups I and II were administered soya oil (2？mL/kg) and vitamin C (100？mg/kg), respectively. Group III was coadministered CPF (4.25？mg/kg ~1/20th LD50) and Pb (250？mg/kg ~1/20th LD50), respectively. Group IV was pretreated with vitamin C (100？mg/kg) and then coadministered with CPF (4.25？mg/kg) and Pb (250？mg/kg), 30？min later. The regimens were administered by gavage for a period of 9 weeks. The marginal decrease in serum triiodothyronine and thyroxine and the significant increase in the concentrations of thyroid stimulating hormone and malonaldehyde in the group coadministered with CPF and Pb were ameliorated by vitamin C partly due to its antioxidant properties. 1. Introduction Man and animals are exposed to a “soup” of chemical contaminants in the environment, which directly or indirectly affect their health and well-being. Pesticides and heavy metals are the most common environmental contaminants because of their respective widespread use in agriculture and industries. Hitherto, most studies on these chemical contaminants have centered on the examination of one single agent and therefore, current understanding of the toxicity of many environmental toxicants/pollutants is based primarily on toxicity studies performed on laboratory animals exposed to a single toxic agent [1, 2]. However, the environment is heavily contaminated with many chemicals, which interact with each other in such a way that modify their toxic response in humans and animals. Organophosphate (OP) compounds are the most widely used insecticides accounting for 50% of global insecticidal use  while Pb is the most widespread heavy metal contaminants with wide applications . Occupational and environmental Pb exposure continues to be among the most significant public health problems [4–7]. Due to their persistent nature in the environment and their toxicodynamics, CPF and Pb have resulted in deleterious effects in man and animals . The toxicity of Pb remains a matter of public health concern  due to its pervasiveness in the environment and the awareness about its toxic effects  at exposure levels lower than what was previously considered harmful . Reproductive consequences of Pb exposure are widespread , affecting almost all aspects of reproduction . Pb induces decreased sperm count and motility and increased
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