Progesterone (P4) is an inductor of the preovulatory surge of LH, while estradiol (E2) acts as a hypothalamic primer to allow P4 receptor development, as well as a stimulator of yolk production. Conversely, the role of testosterone (T) has been more controversial; however, there is now enough evidence, which demonstrates an essential action of T in the ovulatory process.For instance, blockage of endogenous T, by passive or active immunization or by the use of a specific antagonist of T, inhibits ovulation and the preovulatory surges of P4 and LH. This information is supported by the fact that there is a positive correlation between the occurrences of the T preovulatory surge and those of P4 and LH, in which the absence of T
caused a lack of P4 and LH increase in almost 90% of the cases. Additionally, it has been observed that T
has a paracrine action within the ovary, to promote P4 secretion by granulosa cells from the larger follicles.