I am interested to know the process of development of puberty. During puberty, when boys/girls reache 12-14 (puberty) years of their age, their hypothalamus releases gonadotropin releasing hormone (GnRH) and then this hormone in turn affects the pituitary gland which releases FSH and LH. FSH/LH hormones promote male/female features. For e.g. girls start their first menstruation cycle and males start to produce sperm; their voices become smooth and intense respectively. So all these phenomena are dependent on GnRH.My question is that if those hormones are produced due to the effect of GnRH then how is GnRH production itself regulated. In other words how does our body "know" that we are in the age of puberty and it should secrete GnRH?
GnRH-secreting neurons are not fully independent. To date, their most studied regulators are kisspeptin-secreting neurons. During childhood, kisspeptin-secreting neurons are off, due to GABAergic higher level structures and to lack of free leptin. So both brain and body fat have a word on it.
Caveat: most of the evidence is circumstantial (for example, higher circulating kisspeptin in naturally occurring precocious puberty) and I am oversimplifying, so the picture is more complex and will become even more so.