CHEMISTRY OF HORMONES
With respect to their chemical structure, hormones may be classified into three groups: amines, proteins, and steroids.
1. Amines—these simple hormones are structural variations of the amino acid tyrosine. This group includes thyroxine from the thyroid gland and epi-nephrine and norepinephrine from the adrenal medulla.
2. Proteins—these hormones are chains of amino acids. Insulin from the pancreas, growth hormone from the anterior pituitary gland, and calcitonin from the thyroid gland are all proteins. Short chains of amino acids may be called peptides. Antidiuretic hormone and oxytocin, synthesized by the hypothalamus, are peptide hormones.
3. Steroids—cholesterol is the precursor for the steroid hormones, which include cortisol and aldos-terone from the adrenal cortex, estrogen and pro-gesterone from the ovaries, and testosterone from the testes.