Endocrine monitoring for assisted human conception.

The pregnancy potential of an assisted conception treatment cycle increases with the number of oocytes or embryos returned to the patient. It is therefore necessary for the patient to undergo a form of follicular stimulation which will result in the recruitment of a cohort of preovulatory follicles and hence supernumerary oocytes. The commonest superovulation regimen used consists of clomiphene citrate combined with human menopausal gonadotrophins. However the administration of these stimulants increases circulatory levels of LH and perturbs the normal feedback systems of the hypothalamus-pituitary-ovarian axis leading to an attenuation of the endogenous LH surge. The normal and synchronous development of the uterine endometrium may also be impaired which could lead to a failure of implantation. These inherent problems mean that rapid endocrine monitoring facilities are mandatory for optimizing the outcome of the cycle. Recent use of GnRH analogue agonists which effectively reduce tonic levels of LH and inhibit the surge have brought about a significant improvement in pregnancy outcome. However some endocrine monitoring is required even after pituitary desensitisation in order to reduce the incidence of the ovarian hyperstimulation syndrome.