Introduction

Stroids are a class of organic compounds characterized by a specific arrangement of 17 carbon atoms arranged in a tetracyclic structure.

Types

The main types of steroids include:

• 
  
• Corticosteroids: Involved in the immune response and inflammation
  
• Anabolic Steroids: Synthesize proteins and are used in muscle building
  
• Androgens: Sex hormones involved in male characteristics
  
• Estradiol: A form of estrogen
  

Medical Uses

Stroids have various medical applications, including:

• 
  
• Treatment of adrenal insufficiency
  
• Management of autoimmune diseases
  
• Assisted reproductive technologies (ART)
  

Side Effects

Common side effects include:

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• Hormonal imbalances
  
• Increased risk of infections
  
• Development of tumors
  
• Aging changes
  

Legal Status

The use, possession, and distribution of steroids are highly regulated due to their potential for misuse.

# Steroid

## Page version status
This article covers various aspects of steroid molecules, their biological roles, and related research. For detailed information on steroids as part of the broader context of lipid biology or specific applications in medicine, refer to relevant Wikipedia articles.

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## Nomenclature
The name "steroid" derives from the four-ring structure common to all steroid molecules. These molecules are named based on their structure and function. For instance, "Cholesterol" refers to a steroid with a specific functional group that plays a crucial role in animal cell membranes. Similarly, "Estradiol" is a steroid hormone critical for female reproductive health.

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## Rings and functional groups
Steroids consist of four interconnected rings, with each ring containing specific functional groups. These functional groups, such as hydroxyl or ketone groups, influence the steroid's biological activity. The intact ring system is essential for maintaining the molecule's structure and function.

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## Naming convention
The naming convention of steroids typically includes the number of rings (three six-membered and one five-membered), substituents, and the location of those substituents. For example, "Testosterone" has a hydroxyl group at position 2 and a ketone at position 17.

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## Species distribution
Steroids are widespread across the animal, plant, fungal, and bacterial kingdoms. In eukaryotes, they serve diverse functions, while in prokaryotes, their roles often relate to stress responses and energy storage.

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## Eukaryotic
Eukaryotic organisms rely heavily on steroids for cellular structure, hormone production, and membrane stability. Examples include animals, plants, fungi, and certain protists.

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## Prokaryotic
Prokaryotic species also produce steroids, often as part of their membranes or for regulatory purposes. However, the types of steroids in prokaryotes differ significantly from those in eukaryotes.

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## Fungal
Fungi produce a variety of steroids, including ergosterol, which is crucial for their cell membranes.

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## Plant
Plants synthesize sterols, such as sitosterol and lanosterol, for membrane integrity. These are also precursors for important plant hormones like gibberellins.

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## Animal
Animals depend on a wide array of steroids, including cholesterol, sex hormones (like estrogen and testosterone), and vitamin D, which is technically a steroid hormone.

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## Types by function
Steroids can be categorized by their role: some act as structural lipids (e.g., cholesterol), others function as hormones (e.g., aldosterone, estradiol), while still others are precursors for vitamin D or bile acids.

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## By structure
Intact ring systems are the defining feature of steroids. They include the four fused rings and substituents at various positions that determine their activity.

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## Cleaved, contracted, or expanded rings
Steroids can have altered ring structures due to processes like oxidation or enzymatic cleavage. These modifications impact their biological significance and metabolism.

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## Biological significance
The importance of steroids is evident in their roles as lipids, hormones, and precursors for essential molecules like vitamin D and bile acids. Cholesterol, for instance, is a critical component of animal cell membranes.

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## Biosynthesis and metabolism
Steroid biosynthesis begins with the Mevalonate pathway, which produces the precursor HMG-CoA. This molecule is then converted into lanosterol and sitosterol, which serve as building blocks for various steroids. Steroidogenesis involves the oxidation of these precursors to form active steroid hormones.

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## Catabolism and excretion
Cells regulate steroid levels through catabolism (breakdown) and excretion. For example, animals excrete excess cholesterol via bile salts. This process is tightly controlled by biological clocks and metabolic regulatory networks.

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## Isolation, structure determination, and methods of analysis
The isolation of steroids often involves extraction techniques like column chromatography or gas chromatography-mass spectrometry (GC-MS). Advanced spectroscopic methods are used to determine their three-dimensional structures.

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## Chemical synthesis
Steroid synthesis can be achieved via semisynthesis from natural precursors or through total synthesis from simpler molecules. Lanosterol and sitosterol are common starting points for semisynthesis, while sterols derived from cholesterol are often synthesized for industrial applications.

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## Research awards
Numerous Nobel Prizes have been awarded to researchers contributing to our understanding of steroid biology and metabolism. Notable laureates include Earl Sutherland Jr., who discovered cortisol's role in inflammation, and Christian de Duve, who studied lysosomal function and sterol dynamics.

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## See also
- **Lipids**: Overview of lipid classes.
- **Hormones**: General discussion on hormones.
- **Biosynthesis**: Detailed processes in cellular metabolism.

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## References
1. Wikipedia article on Steroid (to be cited appropriately).
2. Source for Mevalonate pathway details.
3. Reference on steroid catabolism and excretion mechanisms.

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