* A protein called alpha-fetoprotein binds oestradiol to prevent it from crossing the blood brain barrier, therefore oestradiol cannot effect the [[Hypothalamus_-_Anatomy_%26_Physiology|Hypothalamus]]. | * A protein called alpha-fetoprotein binds oestradiol to prevent it from crossing the blood brain barrier, therefore oestradiol cannot effect the [[Hypothalamus_-_Anatomy_%26_Physiology|Hypothalamus]]. |