Prohormones are precursors to parent hormones such astestosterone, nor-testosterone, nandrolone. These hormones are converted toparent hormones via liver enzymes. Prohormones are used mainly by athleteslooking to increase size, strength, endurance, reduce recovery time or add leanbody mass. They are most often used for increasing muscle mass or reducing bodyfat levels.

Pro-hormones, and/or Pro-steroids (I won't get into all thesubdivisions and categories since there are many and they all work more similarlythan you're led to believe) are essentially weak steroids.  Many of them were once legal, but are nowgone. No doubt about it, they worked, not as well as pharmaceutical gradesteroids, but better than most nutritional supplements. Pro-hormones areprecursors of certain natural or synthetic anabolic androgenic steroids (AAS).They are often referred to as 'natural' alternatives to AAS.

Prohormones can have the same side effects as anabolicsteroids, and are dependant upon the user as to which side effects one mightexperience. Some side effects are acne, hair loss, breast tissue enlargement,and prostate swelling. Prohormones are substances that are enzymaticallyconverted to anabolic hormones in the body. They are differentiated fromanabolic steroids in that enzyme conversion is a rate limiting factor in howstrong of a response they illicit.

Oral delivery is the easiest but is usually associated withthe lowest bioavailability and a higher possibility of liver toxicity. Also,oral use necessitates dosing 3-4 times daily as it only keeps blood levelselevated for a few hours. Oral steroids have a 17aMethyl group which blocksliver enzymes and therefore can cause liver enzymes to increase. Often greymarket anabolic steroids like the prohormones (ones not classified by the DEA,yet not legal by FDA standards) use this 17a Methyl delivery system to increasepotency.

Prohormones and steroids cannot be taken year round, but arerather run in short "cycles" by bodybuilders and other athletes.  This is especially true of the oral steroidsbecause of their effect on the liver and liver enzymes.

Cycling is assumed to have three purposes: to optimizeresults in a given training phase; to prevent harmful side effects by givingthe body a rest; and to overcome the body’s tolerance for the supplements.Typical supplementation cycles run between four and 12 weeks.  Finally, it is especially important to takeadequate time off after each cycle with these substances to allow the body torecover and to follow a proper post cycle therapy.