Now that I think about it, our family MD, a middle-aged man, always had me pull down my own pants and underwear when he wanted to check me for a hernia.
But if I had a rectal temperature taken or had to receive a shot, which was always done by one of his nurses, the nurse would usually strip me herself... though in the case of an RT, with me lying on the table and crackling paper, it seems like it would have made more sense to ask me to do it. The way I remember it, I would be lying on my back, and then she'd say, "I need to take your temperature," and her fingertips would go to my belt, unbuckle it, unzip me, and open my pants. Then, she'd ask me to turn onto my tummy, I'd comply, again to a crackle of the paper and a jingle from my belt (I'd move the buckle out of the way), and she'd pull down my underwear to just past my hips. Even then, I liked her hand on my hip, and the feeling of the Vaseline on my anus before the thermometer slid in.
With shots, I was usually standing, and the nurse would likewise unbuckle me (reaching around me to do this), unzip me, open up my pants and let them fall, and then pull down my briefs to just past my hips. If I had on a shirt with tails, she'd lift it and have me hold it in place with my underarms.
I do remember a few times, though, when I got a shot in the front, with the nurse having me lie on my back in the table, opening and sliding down my pants and my underwear ("Raise up...") until they were past my hips and penis, then giving me the injection in the crease between my belly and thigh.
Even as a kid, I wondered about something else: which was why, during shots I took while standing, some nurses would just slide down my underwear in the back, letting the elastic band rest under my hips, but others would pull them down to a uniform latitude, so that everything showed, including my penis being bare, in the front. Making me essentially naked didn't seem necessary, for the shot.
It never occurred to me at the time that some nurses might like stripping the pants off boys, and I'm very doubtful that that was ever the case with the nurses who stripped me. But to this day, the feeling of having my pants pulled down to just past my hips, whether just in the back or with my cock laid bare, as well, is very erotic.
And I love it during massages, when the masseuse is working on my lower back, and the sheet is gradually pushed down by her moves, so that I can feel increasing amounts of my hips and crack being exposed to the air, and her gaze. If she turns away for a moment to replenish her oil, or to load a hot towel, I surreptitiously touch myself in back to see just how much of my crack is exposed. The best times are when she just slides down the sheet to past my hips entirely.