Hormones can be classified into different groups based on their chemical structure and function. The main classes of hormones include:
- Peptide and Protein Hormones:
- These hormones are composed of amino acids. Examples include insulin (regulates blood sugar), growth hormone (stimulates growth and development), and oxytocin (involved in childbirth and lactation).
- Steroid Hormones:
- Steroid hormones are derived from cholesterol. They include hormones such as cortisol (regulates stress response and metabolism), testosterone (male sex hormone), and estrogen (female sex hormone).
- Amino Acid Derivative Hormones:
- These hormones are derived from amino acids. Examples include thyroid hormones (thyroxine and triiodothyronine), which regulate metabolism, and adrenaline (epinephrine) and noradrenaline (norepinephrine), which are involved in the “fight or flight” response.
- Lipid-Derived Hormones:
- These hormones are derived from lipids. Prostaglandins, for example, are lipid-derived hormones that play a role in inflammation, blood clotting, and various physiological processes.
- Gaseous Hormones:
- Nitric oxide is an example of a gaseous signaling molecule that acts as a hormone. It plays a role in vasodilation, neurotransmission, and immune response.
- Neuropeptides:
- Neuropeptides are a class of peptides that function as neurotransmitters in the nervous system and also act as hormones when released into the bloodstream. Examples include substance P and endorphins.
- Paracrine and Autocrine Regulators:
- While not traditional hormones, paracrine and autocrine signaling molecules have hormone-like functions. Paracrine regulators act on nearby cells, and autocrine regulators act on the same cells that produce them. Local signaling molecules, such as cytokines, growth factors, and prostaglandins, fall into this category.
- Melatonin:
- Melatonin is a hormone produced by the pineal gland in response to darkness. It regulates the sleep-wake cycle and has antioxidant properties.
These groups represent a broad classification, and individual hormones within each group can have diverse functions and effects on various physiological processes. Hormones work together in intricate networks to maintain homeostasis and regulate the body’s functions. The classification of hormones helps in understanding their chemical nature, mechanisms of action, and roles in physiological processes.