3. HCG
hormone secreted by the embryo which maintains luteal secretions
in case of an implanted pregnancy..
4. OESTROGENS
secreted by the growing follicle and by the corpus luteum.
5. PROGESTERONE
produced after ovulation by the corpus luteum.
Thus,
in a natural cycle, only one oocyte matures each month under
the action of various hormones, while the uterus is prepared
to accommodate an eventual pregnancy.
In IVF, however, the growth and maturation of several
follicles and oocytes is artificially stimulated
through appropriate
hormonal treatment.
This is aimed at maintaining and stimulating additional
follicles which would otherwise have regressed.
