The organizational processes occuring in utero and during early development set the stage for adrenarche, a rise in adrenal steroids beginning between the ages of 6-8 years that is associated with the development of axillary and pubic hair (Patton & Viner, 2007). Gonadarche is initiated in a separate process by the increasing activation of specialized hypothalamic neurons that secrete gonadotropin releasing hormone (GnRH), typically occurring between ages 8-13 in females and between 9-14 in males (Euling et al., 2008; Senzaki et al., 1993). The rise in GnRH stimulates increased secretion of lutenizing hormone (LH) and follicle-stimulating hormone (FSH) from the pituitary, triggering the rise of output of the gonadal steroids estradiol and testosterone, which in turn brings about the somatic events associated with sexual maturation. Studies of twins indicate that 60-80% of the 4-5 year variation in onset of gonadarche may be due to genetic factors (Silventoinen et al., 2007; van den Berg & Boomsma, 2007). Physiologic and environmental signals appear to have more of a permissive role that prevents pubertal onset in the presence of adverse conditions such as
