During the natural menstrual cycle both FSH and LH play important roles in the follicular phase, securing follicular growth and development resulting in competent oocytes capable of sustaining further development. It is well known that after an initial FSH rise in the early follicular phase, FSH becomes down-regulated in the middle of the follicular phase, while the concentration of LH remains relatively constant throughout the follicular phase. Selection of the dominant follicle takes place around the mid-follicular phase at a diameter of 8-10 millimetre. The selected follicle starts to develop LH receptors on the granulosa cells, while FSH receptor expression continues to decline until ovulation [1,2]. Thus, in the second half of the follicular phase both gonadotropins advance follicular growth with a key contribution from LH. In connection with ovarian stimulation (OS) and ART treatment, most protocols use either a GnRH-agonist or a GnRH-antagonist to secure low pituitary output of gonadotropins, especially LH. Therefore, OS protocols don’t mimic normal physiology and usually provide supraphysiological concentrations of FSH, while LH/hCG typically is considerably lower than physiological concentrations. Thus, what are requirements of LH/hCG and should a lower threshold concentration be surpassed or preferentially be in the physiological range to improve IVF outcome? Many different meta-analyses have compared the use of HMG and FSH for OS to answer this question, but depending on inclusion criteria different results have been obtained – one favouring one conclusion over the other, while the opposite conclusion remains a valid option.