Ovarian stimulation for in-vitro fertilization: clomiphene and HMG.

Details of the problems and successes obtained after various forms of hormonal stimulation in an IVF programme are presented. The endocrine conditions normally existing in the natural menstrual cycle are discussed first, followed by analyses of the types of responses to clomiphene, clomiphene and HMG, HMG alone and LHRH agonists. Clomiphene produces fewer embryos than other treatments but gives a good control of follicle growth and ovulation. Clomiphene and HMG increases the number of available oocytes, and this raises the chance of pregnancy, but there is a greater heterogeneity in the follicular population. HMG alone is suitable for most conditions except for those with PCO syndrome and gives an average of six oocytes per treatment cycle. The problems associated with premature rises in levels of LH are overcome by using LHRH agonists with HMG, and this results in satisfactory numbers of oocytes but requires endocrine support in the luteal phase. The need for luteal phase support after various therapies remains unclear, and a calculation of the ratios between various steroids may help to clarify the need for it.