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 Oxandrolone hormone does not carry any estrogenic related side effects. It does not aromatize and cannot lead to gynecomastia or water retention due to increases in estrogen levels. It further carries no progestin related activity, which again supports no estrogenic related side effects. Due to water retention being impossible with this steroid, this will decrease the risk of high blood pressure. Excess water retention can promote high blood pressure. Some steroids that do not aromatize can lead to high blood pressure, such as Trenbolone , but Anavar is rarely associated with this trait.