Gonadotrophin-releasing hormone is the controlling factor for the two gonadotrophic hormones, LH and FSH. It is released in a pulsatile fashion varying in frequency and amplitude during the menstrual cycle. Gonadotrophin-releasing hormone analogues are modifications of the native molecule of GnRH and have much increased potency than native GnRH and when administered, they produce continuous stimulation of GnRH receptors of the gonadotrophes, leading to down regulation of these receptors and suppression of gonadotrophic secretion. They are used in the treatment of endometriosis, adenomyosis, decreasing the tumour size in uterine leiomyomata, endometrial hyperplasia, dysfunctional uterine bleeding, premenstrual tension syndrome, central precocious puberty, hormone dependent cancers and in assisted reproductive technology and in vitro fertilization. Add-back therapy is used for treatment of side effects that occur from this hypoestrogenic state as estrogen replacement therapy and other medications.