Secular trend of timing of puberty.

During the last decades, a secular trend of growth and timing of puberty occurred consisting of increased adult height and earlier onset of puberty. In The Netherlands although the most recent survey showed an increase of final height again, the timing of puberty onset appears to level off, and in boys pubertal onset was even slightly retarded. Different findings were reported from the United States, where a strong advancement of the onset of puberty was observed in both white and black girls, although the effect was more evident in black girls. Timing of puberty follows a familial pattern and therefore seems to be controlled by genetic factors, whereas environmental factors may influence and mediate the genetic regulation. Environmental factors such as nutritional status, chronic diseases, migration to a healthy environment, frequent infectious diseases, pollution and exposure to insecticides are all thought to influence the endocrine regulation status and therefore differentiation and development of endocrine organs. In this chapter, the physiologic mechanisms of puberty onset with the different regulatory aspects, as well as pathologic processes interfering with the onset of puberty will be discussed.