Amino Acid-Derived Hormones

The amino acid-derived hormones are relatively small molecules that are derived from the amino acids tyrosine and tryptophan, shown in Figure 1. If a hormone is amino acid-derived, its chemical name will end in –ine. Examples of amino acid-derived hormones include epinephrine and norepinephrine, which are synthesized in the medulla of the adrenal glands, and thyroxine, which is produced by the thyroid gland. The pineal gland in the brain makes and secretes melatonin which regulates sleep cycles.

Part A shows the amino acid tyrosine on the left and epinephrine on the right. Epinephrine is similar in structure to tyrosine, with minor modifications. Part B shows the amino acid tryptophan on the left and the structurally similar melatonin on the right.

Figure 1. (a) The hormone epinephrine, which triggers the fight-or-flight response, is derived from the amino acid tyrosine. (b) The hormone melatonin, which regulates circadian rhythms, is derived from the amino acid tryptophan.