GnRH (gonadotropin-releasing hormone) is a peptide hormone synthesized and released by the nucleus arcuato located in the hypothalamus. The released GnRH then passes into the pituitary gland through the portal system and performs its function: to stimulate the production of FSH and LH.
Among its most relevant characteristics we highlight that GnRH has a pulsatile secretion, that is, it is released through pulses of different amplitude or frequency depending on the moment of the menstrual cycle in which the woman is. For example, the frequency of pulses in an adult woman is about 90-100 minutes in the early follicular phase, while in the late follicular phase a pulse is released every 60 minutes. In men, on the other hand, the pulses are of constant frequency.
Another important aspect of GnRH is that it has a half-life of 2-4 minutes, so it cannot be detected in peripheral blood.