Follicular fluid is a vascular compartment within the mammalian ovary, separated per follicular stroma by the follicular wall that constitutes “blood-follicle barrier”. The follicular fluids also contain molecules implicated in follicular cell proliferation and differentiation. Follicular fluid consists of various nutrients, growth factors, hormones, electrolytes and enzymes and plays a key role in the physiological, biochemical and metabolic aspects of the maturation process of the oocyte. The knowledge regarding the biochemical composition of the follicular fluid can provide useful information about the requirements for cell and oocyte growth and maturation which may be used as a provisional guide for formulating suitable culture media for in vitro cell culture and oocyte maturation in a particular species. Varying degree of steroid hormonal concentration in the follicular fluid is related to size, growth of follicle, stage of estrous cycle and healthy and atretic state of the ovarian follicles. Thyroid hormones due to their general metabolic and permissive effects are essential for normal ovarian activity in mammalian species.