Figure 40.2 Three Classes of Hormones (A) The largest hormone molecules are peptides and proteins. An example of a protein hormone is the pancreatic hormone insulin. (B) Steroid hormones are modified from cholesterol molecules. They include the corticosteroids produced by the adrenal gland and the sex steroids produced primarily by the gonads. (C) Amine hormones are tiny molecules synthesized from a single amino acid. Both epinephrine and thyroxine are synthesized from tyrosine units, but thyroxine is lipid- r-