[header] How to study the functions of protein hormones in humans [title] Define protein hormones. [step] Protein hormones are a type of chemical compound in the body that regulate metabolism and cell function. They are derived from amino acids (the building blocks of proteins) and facilitate signaling between cells of the endocrine system and various other cells of the body. 
[substeps] Hormones regulate a number of biological processes such as muscle growth, heart rate, hunger, and menstrual cycles. Proteins are a class of biochemical compounds found in the body of all living systems.