Steroid Hormones



Steroid hormones are one the major types of hormones in the body, and include sex steroids like testosterone and corticosteroids like aldosterone. Steroid hormones are made from a cholesterol backbone, and are synthesized primarily in the smooth endoplasmic reticulum. Just like cholesterol, steroids have a characteristic 4-ring chemical structure. Due to their origin from cholesterol, steroids are fat-soluble, or hydrophobic molecules, and require a carrier protein to move in the blood. However, once they reach the target cell, they can directly pass through the cell membrane to enter the cell, and act directly upon receptors inside the cell, such as those in the cytoplasm or nucleus. The action of steroid hormones on intracellular receptors alter the transcription and translation of proteins to cause downstream effects.

Key Points

  • Steroid Hormones
    • Derived from cholesterol
      • Cholesterol is a type of lipid, so steroid hormones behave like fats
        • Steroids and Cholesterol have a 4-ring structure
      • Formed in the Smooth Endoplasmic Reticulum
        • Also produced in mitochondria to some extent
    • Hydrophobic (fat-soluble)
      • Require carrier protein to move in blood
    • Pass through cell membrane
      • Act as primary messengers on receptors inside cell
        • Receptors may be in the cytoplasm or nucleus
      • Affect transcription/translations of proteins