There is a wide range of hormones available for hormone replacement therapy. Hormones are usually available in the following forms:

• Tablets. Tablets are the most popular method for administering oestrogens, progesterone, and anti-androgens. They have the advantage of being readily available from most chemists. Scripts for hormone tablets usually last for a couple of months or more, so if you hate the idea of fronting up to your doctors surgery every five minutes, then they are a very good idea. On the down side, though, you have to remember to take them regularly, as often as three times a day. Also, risk of liver damage is higher when taking hormone tablets than with other forms.
• Injections. As far as I'm aware, this is the most popular way to administer testosterone. Injections have the advantage of being much more fuss free than having to regularly take tablets, and also pose less of a strain on your body. Unfortunately, you'll have to turn up at your doctors office very frequently for the injections.
• Implants. These are little slugs of medication, that are implanted into one of your muscles, and release hormones slowly, usually over a period of several months. They're effectively a 'set and forget' form of hormone administration. However, only a very limited range of products are available in implant form, and the actual doses for implants are usually much lower than for injections or tablets, so they're only really of use if you're on a low dose, say post operatively, or if you've been on hormones for several years. Also, changing your dose is next to impossible if you have implants. Inserting the implants requires a minor surgical procedure under a local anaesthetic. Not all doctors are keen to do this.
• Patches. These are similar to implants, but are kept outside the body, in self adhesive patches. You usually stick them to your bum, where they won't be glaringly obvious. They usually need to be replaced twice a week or so. Many people report skin irritations due to the patches, and they aren't available in large doses. Also, you may get unwanted questions from sexual partners.

For the male to female transsexual, there are three hormone groups that you will be interested in. These are:

• Oestrogens. As discussed earlier, oestrogen has a gradual feminising effect. Common brands are Premarin, Estigyn, Progynova, and Ogen.
• Anti-Androgens. These chemicals have the effect of reducing production of, or effectiveness of, natural androgens (testosterone). The usual way this is done is to introduce a chemical which ‘looks like’ testosterone, but doesn’t work. In this way, testosterone receptors become clogged up with this chemical, and thus the testosterone in your body has less effect. Also, the endocrine system is fooled into thinking that your body has too much testosterone, so shuts down production. Anti-Androgens are very useful for combating problems with body hair and masculine sexual urges. Common brands are Androcur and Aldactone. Androcur will make you tend to retain water, so you’ll put on weight. Aldactone has the opposite effect, as it’s a diuretic.
• Progesterone. This hormone is responsible for filling the milk ducts in pregnant women. It tends to make the breasts swell somewhat, and is usually prescribed to overcome problems with nipple soreness. A common brand is Provera.

For the female to male transsexual, the only hormone used is testosterone. This has a dramatic masculinising effect, as discussed earlier.