What can cause delayed puberty in girls?

Multiple causes: Delayed puberty results from disruption of the hormones regulating periods. Often delayed puberty is familial, with a family history of later periods. Weight loss, low weight or intense exercise causing low body weight can disrupt hormonal balance. Occasionally it can be a genetic issue like turner's syndrome. If the delay is significantly past 12 to 13 y old, then a workup is in order.