Oxandrolone is a synthetic androstane steroid and a 17α-alkylated derivative of DHT.    It is also known as 2-oxa-17α-methyl-5α-dihydrotestosterone (2-oxa-17α-methyl-DHT) or as 2-oxa-17α-methyl-5α-androstan-17β-ol-3-one, and is DHT with a methyl group at the C17α position and the C2 carbon replaced with an oxygen atom.    Closely related AAS include the marketed AAS mestanolone (17α-methyl-DHT), oxymetholone (2-hydroxymethylene-17α-methyl-DHT), and stanozolol (a 2,3- pyrazole A ring -fused derivative of 17α-methyl-DHT) and the never-marketed/ designer AAS desoxymethyltestosterone (3-deketo-17α-methyl-δ 2 -DHT), methasterone (2α,17α-dimethyl-DHT), methyl-1-testosterone (17α-methyl-δ 1 -DHT), and methylstenbolone (2,17α-dimethyl-δ 1 -DHT).   
The use of anabolic steroids will suppress natural testosterone. The rate of suppression is dependent on the steroid in question, but in the case of Oxymetholone it is enough to warrant the use of exogenous testosterone. This will actually hold true with most anabolic steroids. Those who supplement with Anadrol and forgo exogenous testosterone therapy will fall into a low testosterone condition. Not only is this a condition that comes with numerous bothersome symptoms, it is an extremely unhealthy state. The form of testosterone you choose when using Anadrol is of no consequence, however, you should ensure you are applying enough to provide what the body needs.
Once the use of Anadrol and all anabolic steroids has come to an end and all the exogenous hormones have cleared your system natural testosterone production will begin again. This is assuming there was no prior existing low level state. It also assumes no damage was done to the HPTA during supplementation due to improper practices. While natural testosterone production will begin again on its own, it will not be fast. It is generally recommended that the individual begin a Post Cycle Therapy (PCT) treatment plan following anabolic steroid use . This will encourage natural testosterone production and speed the healing process up. It will not automatically return you to your previous natural high level on its own; that will take some time. However, it will ensure you have enough testosterone in your body to function properly while your levels continue to naturally rise.