Diagrammatic representation of the changes in the circulating concentrations of LH and FSH in males [•] and females [•] during various pubertal stages and a summary of the factors that increase gonadotrophin secretion and stimulate gonadal maturation. The shaded bars indicate the proportional rise in testosterone and estradiol secretions in males and females respectively. Activation of the positive feedback mechanism of estradiol in females also occurs during puberty