Final answer:
Steroid hormones are lipid-soluble hormones derived from cholesterol, including adrenocortical and sex hormones, which regulate metabolism, osmoregulation, and reproductive functions.
Step-by-step explanation:
Steroid hormones are a group of lipid-soluble chemical messengers that play vital roles in regulating various physiological processes in both vertebrates and invertebrates. Structurally related to cholesterol, from which they are synthesized, these hormones include two crucial subclasses: the adrenocortical hormones and the sex hormones. Adrenocortical hormones, such as aldosterone and cortisol, are primarily produced by the adrenal glands and are involved in metabolism and osmoregulation. Meanwhile, sex hormones like estrogen and testosterone, produced by the gonads (ovaries and testes), are crucial for reproductive functions.
Due to their hydrophobic nature, steroid hormones can easily diffuse across the plasma membranes of their target cells. Once inside, they bind with specific receptors to form a complex that can enter the nucleus, influencing gene expression and acting as transcription factors. Consequently, their effects are long-lasting compared to those of peptide hormones, such as epinephrine, whose amino acid-based structure results in a much shorter half-life.