Mechanism of action of steroids hormones
Steroid hormones are a class of hormones derived from cholesterol and include hormones such as cortisol, aldosterone, and sex hormones like estrogen, progesterone, and testosterone. They act on cells by binding to specific receptors in the target cell, which can be located in the cytoplasm or nucleus. The mechanism of action of steroid hormones involves the following steps:
1. Hormone secretion: Steroid hormones are synthesized and secreted by specialized endocrine glands in response to specific signals or stimuli.
2. Hormone transport: Once secreted into the bloodstream, steroid hormones bind to specific carrier proteins that help transport them to their target tissues.
3. Diffusion across cell membrane: Steroid hormones are lipid-soluble molecules that can easily diffuse across the cell membrane of target cells.
4. Receptor binding: Inside the target cell, the hormone diffuses into the cytoplasm and binds to its specific receptor. This receptor-hormone complex is usually found in the cytoplasm or nucleus.
5. Formation of hormone-receptor complex: When the hormone binds to its receptor, it induces a conformational change in the receptor, activating it.
6. Translocation into the nucleus: The activated hormone-receptor complex translocates into the nucleus and binds to specific DNA sequences called hormone response elements (HREs) within the promoter region of target genes.
7. Gene expression regulation: Once bound to the HREs, the hormone-receptor complex modulates the expression of target genes by either promoting or inhibiting their transcription. This leads to the synthesis of new proteins or the inhibition of specific gene products.
8. Cellular response: The altered gene expression results in various cellular responses, such as changes in metabolism, cell growth, immune response, or reproductive functions, depending on the specific steroid hormone and target tissue.
Overall, the mechanism of action of steroid hormones involves the binding of the hormone to its specific receptor, translocation of the hormone-receptor complex into the nucleus, regulation of gene expression, and subsequent cellular response. This mechanism allows steroid hormones to exert their physiological effects on target tissues.