So I started DIY a few months ago using estradiol gel for monotherapy (2.5g 0.06% gel applied scrotally twice a day for a total of 3 mg estradiol / day). I saw plenty of expected effects, including nipple sensitivity and no more spontaneous erections (after a month or so even direct stimulation was starting to get less effective). No blood tests, but I conclude estrogen levels are probably OK-ish and testosterone must be somewhat suppressed.
This month, I get on prescription injections instead at last. The standard course here is monotherapy, 10 or 20 mg estradiol valerate (Progynon) as an IM depot injection every two weeks. Different schedules, progestogens, anti-androgens etc are available but I'm probably going to have to advocate for that myself if necessary. First injection, 10mg; I stopped using gel that day. All seems OK, but a few days in, I start getting erections at night again. Weird, but I assume it could be an occasional thing. By day six, they're happening every night, sometimes getting semi-hard during the day too. Nipple sensitivity has pretty much gone so I conclude the injection has worn off and go back on gel. Everything reverts to "gel normal" as above.
Injection two, two weeks after the first, I get 20mg this time. Stop gel again. After a few hours, boom lots of breast sensitivity / swelling. I'm guessing this is a pretty good indicator of E levels. That's slowly dropped down to gel-like levels over the subsequent few days and what do you know, the erections are back again. I conclude peak levels were a bit higher than gel, but dropping off rapidly again and probably not going to last the full two weeks. (This is consistent with the simulator on transfem science).
I'll be asking for blood tests next time and checking with the doctor, but I'd like to get a straw poll: does anybody see random erections even with T suppressed? Am I overthinking things? I'm not seeing a massive return of BO or anything, so I assume T isn't getting that high, but god damn I hate waking up to that thing.