Final answer:
Thyroid hormone is unique as it is composed of the amino acid tyrosine, which is modified and combined with iodine to form the thyroid hormones thyroxine (T4) and triiodothyronine (T3).
Step-by-step explanation:
The student asked which two amino acids compose the unique monoamine structure of thyroid hormone. Thyroxine (T4) and triiodothyronine (T3) are amino acid-derived thyroid hormones produced by the thyroid gland. They derive from tyrosine, one of the amino acids, and require iodine for their synthesis.
Specifically, thyroxine (also known as tetraiodothyronine, T4) is the more abundant but less potent form of thyroid hormone compared to T3 and is often converted to triiodothyronine (T3) by target cells. The thyroid hormones play a crucial role in regulating metabolism and an upregulation of hormone receptors usually occurs in response to chronically reduced levels of a hormone.