What is a characteristic of steroid hormones?

Steroid hormones are characterized by their lipid-soluble nature. This lipid solubility allows them to easily pass through cell membranes, which are also composed of lipid bilayers. Once inside the target cells, steroid hormones can bind to specific intracellular receptors, leading to changes in gene expression and subsequent biological effects.

In contrast, substances that are water-soluble typically cannot cross cell membranes as easily as lipid-soluble substances, requiring different mechanisms, such as binding to membrane receptors. Steroid hormones are not made up of amino acids; instead, they are synthesized from cholesterol, which is a lipid. Finally, steroid hormones are secreted by endocrine glands, not exocrine glands, which release their products into ducts or onto surfaces. Hence, the defining characteristic of steroid hormones being lipid-soluble is fundamental to their function in the body.