Tiny pieces of plastic, widely found in food, water, and air, can harm the development and function of specialized brain cells that regulate reproduction, new research reports. These cells, called gonadotropin-releasing hormone (GnRH) neurons, act like main switches for puberty and fertility. During early development, they must travel to the right place in the brain and then release hormones in a precise rhythm throughout life. However, in a study recently published in the journal Small, researchers found that polystyrene nanoplastics " fragments thousands of times smaller than a grain of sand " were able to slip into these cells through an unusual "side door." Once inside, the particles reduced hormone levels, slowed cell movement, and altered genes required for reproductive health. The particles also accumulated in the GnRH neurons, increasing the potential for long-term effects. The results point to plastic pollution as a plausible environmental contributor to disorders such as GnRH deficiency, which is associated with conditions such as delayed puberty and infertility that cannot be fully explained by genetics alone. "These results suggest that [polystyrene nanoplastics] disrupt key physiological functions of GnRH neurons and may act as novel endocrine disruptors, contributing to the pathogenesis of reproductive disorders," the researchers wrote. Even small disruptions can delay puberty, disrupt menstrual cycles, reduce sperm production or impair fertility.