Final answer:
The three main classes of hormones are peptides, amines, and steroids, distinguished by their chemical structures and solubility, with peptides being chains of amino acids, and steroids being lipid-soluble.
Step-by-step explanation:
The three main classes of chemicals that act as hormones are peptides, amines, and steroids. These different types of hormones are classified based on their chemical structure. Lipid-derived hormones such as steroids can diffuse across plasma membranes due to their solubility in fats, while peptide hormones, composed of chains of amino acids, and amino acid-derived hormones, which are usually smaller molecules, are not fat soluble and cannot diffuse through plasma membranes.
Peptide hormones include substances like those from the hypothalamus and pituitary gland, as well as gastrointestinal mucosa hormones. Steroid hormones comprise those from the adrenal cortex and gonads, including hormones involved in hormonal contraception methods. Finally, amino acid-derived hormones include catecholamines like epinephrine and norepinephrine, and thyroid hormones such as thyroxine and triiodothyronine. This diversity in hormone classes allows for a wide range of functions, targeting various receptors and affecting numerous physiological processes.