The understanding of the steroid stages in the ovarian tissue visually demonstrates that progesterone in the follicular phase, specifically at the phase end, is neither only intermediate nor a side product of the of estrogen synthesis, but it is likely presented as an independent important agent with a specifically designated role. In turn the progesterone serum concentration increase at the end of the induction phase in IVF protocol occurs frequently. The understanding of the fact that the mechanism of progesterone increase is turned on by the super-ovulation induction, known as an obligatory stage of the classical IVF, the following researches aiming to decode it demonstrated that the likelihood of high progesterone registration at the end of the first phase of the IVF cycle is directly correlated with the intensity and duration of stimulation with FSH. The role of LH in the descent of the follicular hyperprogesteronemia is ambiguous. Opposite to the earlier views it is possible that the excessive LH also contributes to the progesterone accumulation or does not play a significant role in progesterone level forming at the end of the follicular induction phase. In the context of the ongoing discussions and a number of unresolved principal questions, one should note that the serum profiles of progesterone throughout the ovarian stimulation can and must be predicted. Considering the same practical view at this stage it is possible to make the following conclusion: all patients regardless of their individual characteristics within a cycle require the measurement of progesterone at the end of the protocol.