Physiology Endocrine Changes		We don't really know what triggers puberty. We do know that the initial change comes from the hypothalamus. It's a result of complex, hormonal interaction between gonadotropins, thyroid hormone and growth hormone. We get an increased pulsatile release of gonadotropin-releasing hormone (GnRH) from the hypothalamus. Subsequently, we have an increase in FSH and LH and then increased synthesis and release of the sex hormones, estrogen and testosterone, to produce the secondary physical sexual characteristics. Independently of the hypothalamic-pituitary-gonadal axis are some of the adrenal changes that we see - that's where our body odor and hair comes from. Then we have a transient insulin resistance which, along with growth hormone, allows for the tremendous skeletal growth that we see during the growth spurt. There are also bone maturational changes that occur, primarily due to estrogen effects. Return to top of page