Estrogen is considered which type of hormone?

Estrogen is categorized as a steroid hormone because it is derived from cholesterol and has a characteristic four-ring structure. Steroid hormones, including estrogen, are lipid-soluble and can easily pass through cell membranes to bind with intracellular receptors. This binding leads to a variety of physiological effects, such as the regulation of the menstrual cycle, the development of secondary sexual characteristics, and contributions to reproductive and metabolic functions.

In contrast, amino acid derivatives, peptide hormones, and protein hormones are different classes of hormones. Amino acid derivatives are synthesized from single amino acids, such as thyroxine derived from tyrosine. Peptide hormones consist of short chains of amino acids, while protein hormones are composed of longer chains and often fold into complex structures. Estrogen's chemical structure and mechanism of action align with those of steroid hormones, distinguishing it from these other categories.