The ovaries need 2 hormones to carry out a correct folliculogenesis (development of the follicle and the oocyte contained in it). These are FSH and LH.
In any ovarian stimulation treatment, whatever the type (antagonists, agonists...) an endogenous LH deficit is induced iatrogenically. Under normal conditions, even if this reduction in LH levels occurs with respect to a natural cycle, the small amount of hormone left circulating in the blood is sufficient. Only 1% of the LH receptors in the follicles need to be activated in order to carry out correct folliculogenesis.
However, there are two groups of patients in whom this deficit may prevent correct follicular development:
- Women over 35: As the years go by, the LH produced by the body is less powerful and the LH receptors are less functional.
- Women who, in spite of having good ovarian reserve parameters, have shown a low response in a previous ovarian stimulation cycle. One of the causes, among others, that can provoke this unexpected low response is a genetic variant of LH that makes the hormone biologically inactive. Thus, if we measure the LH levels in the blood they will be normal, but the hormone will not be able to exert its function.
These are the patients in whom it will be necessary to add LH activity in ovarian stimulation, since they do not have enough endogenous LH to complement FSH in folliculogenesis.
Menopur is not exactly LH, but a hormone called HMG (human menopausal gonadotropin). It is obtained from the highly purified urine of menopausal women, because when the ovaries cease to function, high amounts of FSH and LH are produced and excreted in the urine. 75 units of HMG would be equivalent to 4 units of LH plus 10-12 units of hCG. This hCG binds to the same receptors as LH, so it will exert a similar effect to LH.