It contains endocrine glands that synthesize our hormones. But how many hormones do we have? Well, we have many different hormones and all these different types of hormones that we're going to discuss in the next several lectures can be broken down into three categories. We have peptide hormones that are formed from proteins, we have our steroid hormones that are formed from cholesterol and we have tyrosine derivative hormones that are formed from tyrosine amino acids. So let's discuss these three different types of hormones. Let's begin with our peptide hormone.