How do Steroids Work?

Steroid Type
Location
Mechanism
Testosterone
In the testes within the Leydig cells. The Leydig cells are located in the connective tissue (interstitial tissue) between the seminiferous tubules.

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Anabolic Androgenic Steriods
Not applicable

(anabolic androgenic steroids are synthetic hormones which are consumed either orally or via injection)

 

STEROID MECHANISM:

Steroidogenic cells (steroid producing) produce and release their hormonal product. These cells synthesize some cholesterol (the precursor for steroid hormones) and they are also derived from low-density lipoproteins (LDL) that have been internalized into the cell and degredaded by lysosomal enzymes. Regulation of the uptake and degradation of LDL makes it available to steroidogenic cells when hormones are needed.

Synthesizing hormones from cholesterol require a series of enzymatic reactions that are limited to certain steroidogenic organs. These organs are able to produce only the steroid hormone for which it as a complete set of appropriate enzymes. These enzymes that are necessary for the conversion of cholesterol into a steroid hormone are located in specific intracellular compartments (i.e. mitochondria or endoplasmic reticulum). The steroid molecule is then shuttled back and forth between different compartments within the steroidogenic cell for modification until the final secretory product is formed.

Upon formation, lipid-soluble steroid hormones diffuse through the steroidogenic cell's liquid plasma membrane to enter the blood. The rate of secretion is controlled by the rate of hormone synthesis.

Following secretion, steroid hormones diffuse through the steroidogenic cell's liquid plasma membrane to enter the blood. The rate of secretion is controlled by the rate of hormone synthesis.

Following secretion, steroid hormones undergo interconversions within the blood or other organs, where they are converted into more potent or different hormones.

Steroid hormones, which are lipo-philic, circulate in the blood to their target cells reversibly bound to plasma proteins. Some hormones bind to specific plasma proteins (t hat carry one specific type), while other plasma proteins pick up any "hitch-hiking" hormone. Unbound hormones bind with target cells and once bound, it is rapidly inactivated or removed.

To induce their effect, hormones must bind with target cell receptors specific for them to carry out their task. Lipo-philic steroids can easily pass through the surface membrane and bind with specific receptors located inside the target cell.

Hormones influence their target cells by altering the cell's protein activity:

Hormones activate specific genes in the target cell to cause the formation of new intracellular proteins that produce the desired effect, which is the enhancement of the synthesis of new enzymatic, or structural proteins.

Free steroid hormones have a specific binding region (receptor) in the nucleus of their target cell. Each receptor has a specific region for binding with DNA and the hormone.

Receptors exist in multiprotein aggregate in association with proteins of the molecular chaperon machinery. Molecular chaperone machinery ensures proper folding of newly synthesized proteins.

Once the hormone is bound to the receptor, the hormone-receptor complex binds with DNA at a specific attachment site called the hormone response element (HRE). Binding of the hormone-receptor complex with DNA turns on specific genes within the target cell.

 

Activated genes direct the synthesis of new cell protein by producing complimentary messenger RNA. mRNA enters the cytoplasm, binds to a ribosome and mediates the assembly of new proteins.

The newly synthesized protein produces the target cell's ultimate physiological response to the hormone.

 

 

 

 

 

 

 

 

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