Srs minus 1 month: Stop progestins. If taking an oral estrogen, replace it with a parenteral (non-swallowing) delivery; if that is not possible, stop entirely. Most doctors think it will reduce the risk of thrombosis in the several days following surgery when your mobility is severely reduced. Progesterone and all parenteral estrogen administrations are safe to take right up until surgery.
At orchidectomy or srs: Stop all hormones and antiandrogens. In 3 days, resume a low dose of estrogen, preferrably in whatever form you used pre-op (if it was effective) -- unless it was oral: in that case, considering switching to a parenteral delivery. Avoid radically changing the dosage for a while if at all possible. Allow time for adjusting to the abrupt reduction of endogenous androgens (unless one was on an effective GnRH agonist course, in which case gonadal androgen production was already shut down).
If you were taking progesterone or a progestin pre-op, then 2 weeks after testes are removed, resume a low dosage. If it was in the form of an oral progestin, consider switching to progesterone, or a parenteral delivery, if at all possible. Again, try to avoid radically changing the dosage for a while to give your body time to adjust.
After 2-3 months, your endogenous hormone balance should be settled down enough such that you can begin effectively evaluating subtle variations in regimen.
There are dozens of good reasons post-menopausal natal women, and post-op transsexual women take estrogen. The most critical health consideration is bone density. Without estrogen, bones slowly become more brittle and porous over time, exposing one to the possibility of serious hip fractures or other major breaks from even a very small impact. A low dosage of estrogen -- sufficient to retain good bone density -- is very safe to take parenterally for life. If your only delivery option is oral, take it sublingually (under tongue) or bucosally (between cheek and gum) if at all possible. For details on estrogen delivery safety, see the page How are hormones delivered?
Although most pre-ops take progesterone or a progestin for breast growth, that is not the only reason to consider taking it. There are a wide variety of menopausal-type symptoms that many natal women find are successfully treated with progesterone, and it is true for transsexual women as well. Do a quick web search on "progesterone cream" for hundreds of anecdotes about what can be improved with progesterone. Unfortunately, progesterone is very expensive or otherwise difficult to obtain in some countries; in that case, a low-key progestin may be worth a try. See the page Exactly what hormones are available... for a ranking of progestins.
If you are post-op more than a couple of years, and find yourself devoid of energy, stamina, motivation, and libido, even when you are on what seems to be the best possible lifetime estrogen/progesterone regimen, consider this: after ruling out purely psychological issues, you might need a subtle boost of testosterone. As perverse as that might sound after spending years fighting the evil T, some post-ops find that residual endogenous androgen production (mainly from the adrenal glands) is just not quite enough to sustain a high level of activity. Some genetic women have the same problem. If this bothers you enough to do something about it, take a tiny daily dose of testosterone. Unfortunately, it can be difficult to find low-dosage preparations, especially to be funded by your national or commercial health plan. 0.25-1.0mg/day of oral fluoxytestosterone or 0.5-2mg/day oral methyltestosterone can do the trick, but tablets are especially difficult to obtain because of laws meant to prevent the abuse of anabolic steroids. Some people cover at least 3/4 of the active surface of a testosterone transdermal film before wearing it (rotating the barrier as needed), or else open the film and apply a small amount of the gel each day. It is also possible to have a compounding pharmacy add 5-10mg of micronized testosterone to a custom estrogen and/or progesterone capsule or pessary. If you prefer to cycle, take into account that endogenous androgens in genetic women generally peak just before ovulation and again just before menstruation -- that is, on roughly days 13 and 27 of the cycle described below. Testosterone is powerful and tricky stuff -- be careful.
Post-ops rarely find an antiandrogen to be necessary, but as with everything, there are exceptions. If your scalp hair continues to recede after surgery, try a fractional tablet 0.05-0.5mg)/day finasteride for several months. If it stalls the recession, continue taking it for a year, then stop for a few months to see what happens. If recession resumes, then restart the finasteride and consider yourself a lifetime customer.
There is mounting evidence that estrogen receptors can become saturated, temporarily reducing the sensitivity and/or quantity of available receptors. There is also evidence that serum hormone binding globulin (shbg, the estrogen down-regulator) eventually becomes extremely effective in tying up free estrogen in some individuals when they take a continuous and aggressive dosage of estrogen. If either or both of these are true, then giving the receptors and shbg reaction a rest would improve hormone therapy results for some people. In fact, many transsexuals have reported a significant surge in breast development when estrogen dosage is sharply increased after months or even years of a very conservative dosage. In some cases, the surge in development continues for quite a few months if the estrogen is cycled. Development often trails off again after 3-6 months, after which, it seems that another, or longer, rest is called for.
If one has not attained significant feminization (still using breast growth as the most obvious measuring device, but keeping in mind the modest expectations which are required in this matter), and no progress whatsoever is noted after the testes have been removed for 6 months, one can try aggressive cycling for 3 months timed as outlined below. If some development is attained by month 2, then continue at that dosage for 6 months. If there is no development by month 2, rest for a couple of months then try again with double the peak dosages. If nothing, rest another couple of months and try again, with another doubling of dosage.
If one is going to cycle, given the current lack of data to suggest otherwise, one may as well more or less mimic a 28 day female cycle, rather than picking another cycle out of the air. This can be roughly achieved by intramuscular injection of estrogen in oil on day 1, then taking another shot of 1/2 dosage on day 13. Some people will experience menopausal symptoms (hot flashes, night sweats, severe mood swings, etc.) in the days proceeding each shot; if the discomfort is unacceptable, a small, constant dosage estrogen via another route (cream, gel, transdermal, oral) can be used to provide a floor serum estrogen level -- although that pretty much works against the notion of giving the body a rest between floods of estrogen. If using another delivery besides injections, just plot a wave (graph paper helps) with the highest peak on day 1, a dip to about 1/4 dosage on day 6, 1/2 dosage peak on day 13, dip to zero or nearly 0 dosage by day 20, then ramp up again to full peak dosage by day 1 of the next cycle.
If progesterone or a progestin is part of the regimen, it can be cycled by intramuscular injection in oil on day 8, or by ramping it via another route (suppository, pessary, cream, gel, transdermal, oral) from days 1-14 with the peak on day 8. Some say that cycling the progesterone is more important than cycling the estrogen; other say that the progesterone must be constant to best avoid breast cancer. Of course, many variations are possible. There is no formula better for a transsexual than "do what works." If enough people report that a different cycle is more appropriate, that will be reflected here in the future.
Cycling in this manner often results in at least some noticable development for 1-3 months, then the rate of improvement generally trails off in an asymptotic curve. Repeat for up to 6 months at a time with 3 or more months rest (reverting to a very conservative regimen) between. If one does not achieve any result whatsoever from cycling within a few months of starting, it will likely not help to continue the cycling, at least with that form of estrogen.
This experiment is considered by most to be fairly safe if the estrogen is taken parenterally, and there is no history of blood clotting or prolactin problems. Aggressive cycling with an oral estrogen is very risky, as explained in the Dosage section of the page How can the intended effects of hormone therapy be maximized and the dangers minimized?. Aggressive cycling is meant to facilitate bursts in development, and is not appropriate for lifetime maintenance or pre-ops. However, lifetime post-op cycling can be done safely with low, conservative dosages. The effects at low levels are subtle; observe yourself closely to determine what is the most healthy for your individual case.
For reference -- endogenous androgens in genetic women generally peak just before ovulation and again just before menstruation -- that is, on roughly days 13 and 27 of the cycle as defined in this document.
For lifetime maintenance, use the lowest dosages of any hormones or antiandrogens that you can, consistent with skeletal and mental health.