Which of the following does NOT characterize steroid hormones?

Steroid hormones are a specific class of hormones that are indeed characterized by their lipid nature. Being lipid-soluble enables them to diffuse across cellular membranes easily, allowing them to enter target cells where they can bind to intracellular receptors and influence gene expression.

This class of hormones regulates various physiological processes, including metabolism, immune response, and the development of sexual characteristics, which underscores their crucial role within the endocrine system.

In contrast, steroid hormones are not made of amino acids; this distinction places them in a different category from peptide hormones, which are indeed derived from amino acids. This reinforces why the idea that steroid hormones are made of amino acids is an incorrect characterization. Hence, the correct characterization of steroid hormones highlights their lipid nature, ability to diffuse into cells, and their regulatory roles in physiological processes, apart from the fact that they are not composed of amino acids.