Sterol vs. Steroid — What's the Difference?

Sterols, such as cholesterol, are a specific type of steroid that play critical roles in both cell membrane structure and the synthesis of vitamin D, bile acids, and some hormones. Steroids, encompassing a wider variety of compounds, have a core structure of seventeen carbon atoms arranged in four fused rings. They are significant not only for their role in biological processes, such as hormone synthesis and regulation, but also for their medical applications, including anti-inflammatory and immunosuppressive properties.

Sterols are essential for maintaining the fluidity and integrity of cell membranes, particularly in eukaryotic cells. Steroids, on the other hand, include compounds that act as signaling molecules, such as reproductive hormones (estrogen and testosterone), and corticosteroids, which regulate metabolism, immune response, and water and salt balance.

The distinction between sterols and other steroids lies in their functional groups and biological roles. While all sterols are steroids, not all steroids function as sterols; for example, some steroids are precursors to adrenal hormones or act directly as drugs to treat a variety of conditions.

Sterols typically have a hydroxyl group (-OH) at a specific position on the steroid skeleton, distinguishing them from other steroids that may carry different functional groups. This structural feature is key to their role in cell membranes and as intermediates in the synthesis of steroid hormones.

In terms of applications, sterols are often targeted in dietary and pharmaceutical interventions to manage cholesterol levels due to their impact on cardiovascular health. Steroids, including synthetic derivatives, are used in a wide range of therapeutic contexts, from anti-inflammatory treatments to hormone replacement therapies, reflecting their broader functional diversity.