There are two types of hormones known as steroids and peptides. In general, steroids are sex hormones related to sexual maturation and fertility. Steroids are made from cholesterol either by the placenta when we're in the womb, or by our adrenal gland or gonads (testes or ovaries) after birth. Cortisol, an example of a steroid hormone, breaks down damaged tissue so it can be replaced. Steroids determine physical development from puberty on to old age, as well as fertility cycles. If we are not synthesizing the correct steroidal hormones, we can sometimes supplement them pharmaceutically as with estrogen and progesterone. Peptides regulate other functions such as sleep and sugar concentration. They are made from long strings of amino acids, so sometimes they are referred to as "protein" hormones. Growth hormone, for example, helps us burn fat and build up muscles. Another peptide hormone, insulin, starts the process to convert sugar into cellular energy.