Which of the following is not classified as a type of hormone?

Blood glucose is classified as a simple sugar (monosaccharide) and is not a hormone itself. While hormones can influence blood glucose levels—for example, insulin lowers blood glucose, and glucagon raises it—blood glucose is a substance that is regulated by hormones rather than functioning as a hormone.

The other options—amino acid derivatives, polypeptides, and steroids—are all categories of hormones based on their chemical structure. Amino acid derivatives include hormones like thyroid hormones and catecholamines. Polypeptides encompass a wide range of hormones, including insulin and growth hormone, made up of long chains of amino acids. Steroids are lipid-based hormones such as cortisol and testosterone, derived from cholesterol. Each of these categories directly refers to groups of hormones, which makes blood glucose distinctly different from them.