Kathybird, female bb don't always use testosterone - although some do. More "typical' female AAS include oxandrolone (formerly made by Searle as "Anavar", now made by Savient as "Oxandrin" but universally known within physical culture as
Anavar), and stanozolol, more commonly known as Winstrol (even when someone other than Wynthrop Laboratories makes it).
The reason these drugs are generally favoured by women are a) they tend to be less virilizing than testosterone and some of the other AAS favoured by men and b) they are oral (except for Winstrol, which can be pinned or swallowed), so the dosing is easier. Oxandrolone is a fairly pricey drug but women need such low doses when compared with the doses men have to take, the price almost isn't a concern.
There are other AAS women sometimes use - methenolone (either the oral acetate, or the intramuscular enanthate for injection), which is also known as "Primo", short for Organon's old brand "Primobolan", and nandrolone phenylpropionate, which is often referred to as NPP and was another of the former Organon steroids known as Durabolin. Durabolin is the shorter-acting version of the more popular "Deca Durabolin", which although is also a nandrolone ester, in this case the longer-acting decanoate, is more commonly known as simply "Deca" even though the original brand is no longer made.
Real primo is rarer than hen's teeth. I personally have knowledge of at least one batch that was recently (late 2009) tested and found to be fake. I have a funny feeling it was actually trenbolone, which is a veterinary steroid used by some men (and in very small doses, by some women), usually for cutting as a hardener. Primo is not particularly virilizing. Tren is VERY androgenic and hence not usually a good choice for most women. If I sound like I am hedging my answers, I am. Some women get no virilizing sides from ANY steroids as long as they keep their doses low. Others get sides right away at very low doses of ANYTHING they take. These things are very, very individual.
So there they are - anavar, winstrol and primo, the holy trinity of chick-AAS, with NPP as a less frequent player that appears to be gaining a little more popularity of late, and even tren and testosterone are used sometimes, but far less often, in females.
Women also of course are known to use GH (growth hormone), but of course this is not a steroid - but it is a hormone, so I mention it here for completeness.
I am on female levels of testosterone HRT by the way, and the dose of transdermal cream I use - 1 ml of 1% testosterone in a cream base called "Versabase" applied once a day - puts about 10mg of testosterone on my skin daily, of which about 10%, or 1mg, is absorbed into my system, at least according to pharmacokinetic data published by the makers of the male transdermal test gel "Androderm".
The actual amount absorbed transdermally varies with the location used for application, occlusion, moisture content of the skin, temperature and other factors, and you get your blood work tested to see where your levels are when you titrate the dose.
For women, the cream works just fine since we need so little anyway. For men, even a replacement dose is a LOT of cream. A man's test levels are naturally 10-20 times higher than a woman's natural levels are.
For comparison, hubby is on 150mg of testosterone, by intramuscular injection, per week. I obtain 7-10mg of testosterone a week for my own HRT. Both of us maintain levels of testosterone that are just above the upper limit of sex-specific normal on these doses.
Does this help?