FIGURE 9-2 Causal relationship of adrenarche and pubertal maturation.

NOTE: The old model suggests that adrenal androgens produced by adrenarche are necessary for desensitizing the hypothalamus to the feedback effects of gonadal androgens thus allowing testicular production of testosterone to begin to rise. The new model incorporates both genetic and environmental factors in the onset of adrenarche and gonadarche. In addition to variation in the timing of hypothalamic and pituitary maturation, the onset of adrenal production of DHEA/S and gonadal production of testosterone are also related to energy availability, most likely in the form of fat storage. Adrenal production of DHEA/S may also alter hypothalamic-pituitary control of gonadotropins. The pubertal growth spurt is a product of both the onset of testicular production of testosterone and energy available for bone and muscle growth.