Molecular Mechanisms of the Endocannabinoid System with a Focus on Reproductive Physiology and the Cannabinoid Impact on Fertility.

The endocannabinoid system (ECS) is a complex neuromodulatory network involved in maintaining physiological balance through interactions with various neurotransmitter and hormonal pathways. Its key components-cannabinoid receptors (CBRs)-are activated by endogenous ligands and exogenous cannabinoids such as those found in the plant. Although cannabinoids like cannabidiol (CBD) have garnered interest for their potential therapeutic effects, evidence regarding their safety, particularly for reproductive health, remains limited. This review summarizes the structure and molecular mechanisms of the ECS, its role in reproductive physiology-including its interactions with the hypothalamic-pituitary-gonadal axis (HPG axis), gametogenesis, implantation, and lactation-and the possible consequences of cannabinoid exposure for fertility. In addition, we focus on the involvement of the ECS and cannabinoids in breast cancer, highlighting emerging evidence on their dual role in tumor progression and therapy. These insights emphasize the need for further research to better define the therapeutic potential and risks associated with cannabinoid use in reproductive health and breast cancer.