Centro Nacional de Investigaciones Oncológicas (CNIO) Mar 12 2026 The kick off signal for puberty begins in the brain. Specifically, in the hypothalamus, where specific neurons release a hormone that activates the hypophysis, at the base of the skull, which then releases other hormones to start gonad –ovaries or testicles –maturation. This mechanism leading to a fertile organism is the hypothalamic-pituitary-gonadal (HPG) axis. A study by Spain's National Cancer Research Centre (CNIO) has just