Hormones are often described as “keys” that fit perfectly into certain receptor sites throughout your body to “unlock” or perform certain functions. Receptor sites tell the hormones where to do their important work. In your body, the receptor sites for prolactin and oxytocin are established in your breasts during the first several weeks after your baby’s birth. The more you breastfeed, the more receptor sites are created. The more sites that exist, the more milk you can make. This is why you should breastfeed your baby early, frequently, and without formula. In the long run, this will give you more options as you return to work or school.