Prohormone/ja: Difference between revisions

Examples of natural, human prohormones include [[proinsulin]] and [[pro-opiomelanocortin]], but the most widespread prohormones in use are synthetic and labeled as anabolic steroid precursors, used as [[Performance-enhancing substance|ergogenic]] or [[Anabolic steroid|anabolic agents]] for muscle growth. A commonly consumed example of said precursors are [[androstenedione]] and [[androstenediol]], both of which are currently [[Drug Enforcement Administration|banned substances]] in the United States. However, several illegal steroids, such as [[1-Testosterone|1-testosterone]], are still being produced legally under different chemical names, and the majority have not undergone clinical studies.

== Structure ==

[[File:Proinsuline schematic topological diagram.svg|thumb|Proinsulin molecule; schematic, topological drawing. B chain (orange), C-peptide (gray), and A chain (green). The C-peptide is seen to bind to the B and A chains and suppress hormonal expression. When cleavage occurs to produce insulin, the B and A chain are connected by disulfide bonds, while the C-peptide is cut out and discarded.]]

Some prohormones contain structures other than inactive peptide hormones for the purpose of keeping hormone expression suppressed. For example, proinsulin contains an extra non-hormonal chain called C-peptide that binds two insulin peptide chains together, designed to keep both chains inactive by binding to their ends, specifically, their C-domain junctions, which have been proposed to be their site of binding to hormone-expression receptors in the cell. Despite the restrictions it enables, the C-peptide folds the proinsulin chains to make their junction ends accessible to be cleaved by prohormone convertases later, making the folding of the proinsulin chain containing C-peptide essential for the proper cleavage of proinsulin to successfully produce insulin.

== Function ==

However, other inactive proteins travel in their prohormone form, such as [[vitamin D]], also known as calciferol, which can be produced by the human body via sunlight.

The main regulator of prohormone to hormone conversion is [[prohormone convertase]]. Located in the Golgi apparatus, it uses endoproteolytic cleavage to separate peptide hormones from each other and removes extended amino acid residues that hinder the inactive peptides from being active proteins. Because of this role, prohormone convertase is one of the deciding factors for regulation of hormone content in the body, as it has the ability to change an inactive protein with unsubstantial hormonal effect on the body, to a fully active protein with a meaningful hormonal effect.

For [[peptide hormone]]s, the conversion process from prohormone to hormone ([[Protein precursor|pro-protein]] to [[protein]]) typically occurs after being exported to the [[endoplasmic reticulum]] and often requires multiple processing enzymes. [[Proamylin]], which is cosecreted with proinsulin, requires the above three factors and an amidating monooxygenase to convert itself to an active hormone. Some [[Preprohormone|pro-protein precursors]], such as [[preproinsulin]], also go through this process, with the added step of removing a signal peptide by [[signal peptidase]]s, to convert said precursors into prohormones.

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== Uses ==

=== Prohormone supplements ===

The most everyday use of prohormones is as supplements for muscle growth via ergogenic and anabolic agents. Prohormone supplements became popular from 1960 to 2001 and became used unregulated in [[Major League Baseball]] before select prohormones such as androstenedione and androstenediol became banned in the United States' [[Controlled Substances Act|Anabolic Steroid Control Act of 2004]]. Many prohormone supplements that were claimed to impart anabolic or ergogenic effects in men were banned for their poor side effects, commonly in supplements such as in 3β-hydroxy-5α-androst-1-en-17-one, commonly known as [[1-Testosterone|1-testosterone]], which are as follows:

* Acne

* Hair loss

* Increased risk of heart disease

* Kidney and liver dysfunction

* Hypertension

* Impotence

Many prohormone supplements such as 1-testosterone were legal in the United States until reclassified as a [[Schedule III drug|Schedule III]] drug in 2005. However, many illegal prohormones like 1-testosterone are currently being sold legally and marketed by brands such as “Advanced Muscle Science” as 1-androsterone, and are labeled to contain 1-androstenedione-3b-ol,17-one. Only through a recent clinical study has it been shown that the 1-androsterone in the capsules being sold was identified using semi-quantitation and confirmed to be 1-testosterone.