Is paracetamol a neuroendocrine disruptor of the developing sexual brain?

Although paracetamol is considered a safe medication during pregnancy at therapeutic doses, and despite animal studies showing no negative effects or reporting no adverse effects during pregnancy, there are no well-controlled clinical studies demonstrating the safety for both the mother and fetus. Therefore, its use in this situation depends on the physician’s discretion. Its mechanism involves the inhibition of the enzymes cyclooxygenase 2 and 3 (COX-2,3), which modulate pain and inflammation by reducing prostaglandins. However, COX-2 and prostaglandins are also part of the molecular cascade organizing the brain towards a male direction during the prenatal period, and potentially during other periods as well. Herein, we hypothesize that paracetamol, a common medication used to treat fever and pain, may have long-term effects as a neuroendocrine disruptor of the sexual brain when administered during critical periods of development such as pregnancy, and to a lesser extent, during the neonatal, infancy, and puberty periods. Throughout this manuscript, we discuss the effects of COX-2,3 inhibition on the organization of the brain and sexual partner preference, particularly affecting masculinization of the medial preoptic area. We argue how administration of paracetamol in critical periods of plasticity might have an enduring effect on sexual behavior and other motivated behaviors. Impairments in each of these processes can directly impact individuals’ sexual and mental health. We also discuss how sexual experience in adulthood ameliorated the impaired sexual preference of paracetamol-treated males, indicating an interaction between biological and environmental mechanisms. This manuscript is meant to warn professionals that although paracetamol is a very effective and safe drug, it is likely to disorganize the developing sexual brain, probably contributing to what we call iatrogenic sexual diversity.