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Dec 10, 2023

Classification of hormones:- mechanism of hormone action?

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Dec 10, 2023
Hormones can be classified based on their mechanism of action into three main categories:

1. Steroid hormones: These hormones are derived from cholesterol and are lipid-soluble. They can easily cross cell membranes and bind to intracellular receptors in the cytoplasm or nucleus of target cells. Once bound, the hormone-receptor complex acts as a transcription factor, directly influencing gene expression and protein synthesis. Examples of steroid hormones include cortisol, estrogen, and testosterone.

2. Peptide and protein hormones: These hormones are composed of amino acids and are water-soluble. They cannot cross cell membranes and instead bind to specific receptors on the surface of target cells. This binding triggers a cascade of intracellular signaling events, often involving second messengers such as cyclic adenosine monophosphate (cAMP) or calcium ions. These signaling pathways ultimately lead to changes in cellular function. Examples of peptide and protein hormones include insulin, growth hormone, and oxytocin.

3. Amine hormones: These hormones are derived from the amino acid tyrosine and can be either water-soluble or lipid-soluble. Water-soluble amine hormones, such as epinephrine and norepinephrine, bind to cell surface receptors and activate intracellular signaling pathways similar to peptide hormones. Lipid-soluble amine hormones, such as thyroid hormones, act similarly to steroid hormones by binding to intracellular receptors and influencing gene expression.

It is important to note that these classifications are not mutually exclusive, as some hormones may exhibit characteristics of multiple categories. Additionally, the mechanism of hormone action can vary depending on the specific target tissue or organ.

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