On average, girls begin puberty around ages 10—11 and end puberty around 15—17; boys begin around ages 11—12 and end around 16— Role of sex steroids during development—integration. The testes and ovaries become briefly inactive around the time of birth but resume hormonal activity until several months after birth, when incompletely understood mechanisms in the brain begin to suppress the activity of the arcuate nucleus. BPA mimics and interferes with the action of estrogen—an important reproduction and development regulator. Obstetrics and Gynecology Clinics of North America. Pubic hair often appears on a boy shortly after the genitalia begin to grow. Conversely, menarche may be slightly later when a girl grows up in a large family with a biological father present. American Journal of Obstetrics and Gynecology.