In boys, the testes increase the production of testosterone. In girls, the ovaries increase the production of estrogen and progesterone. These hormones are responsible for the secondary sexual characteristics that develop during adolescence. Physical Changes in Girls
For girls, the 1991 curriculum focused heavily on the menstrual cycle, often utilizing high-quality diagrams and nascent computer-generated graphics to explain: In boys, the testes increase the production of testosterone
Puberty: Sexual Education For Boys and Girls (1991) (original title: Sexuele voorlichting In boys, the testes increase the production of testosterone
Understanding the gradual development of breast tissue and the need for appropriate support (bras). In boys, the testes increase the production of testosterone