why are steroids so useful as signaling molecules?
why are steroids so useful as signaling molecules?
Hormones released into the bloodstream from endocrine gland cells and special cells in the hypothalamus (neurosecretory cells) travel throughout the body looking for target cells. Hormones can be classified into three different groups based on their chemical composition:
- Amino acid derivatives
- Peptide hormones
- Steroid hormones
They all have different mechanism of action due to their distinct chemical properties.
Steroids: They are synthesized in a series of reactions from cholesterol and released immediately (constitutive secretion). Generally, they are non-polar and requires carrier proteins to travel in blood. Bind to intracellular receptors to change gene expression directly. Alterations in gene expression; slower onset but longer duration than peptide hormones.
Examples: Cortisol, aldosterone, estrogen, progesterone, testosterone.
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