Miss, I'm sorry to hear your son has adhd. I'm sure he has huge talents too!
Yes I was a "late developer." I completely understand what you mean. At 12 I was avidly glued to the archers and most r4 progs whole contemporaries had pop posters on their walls. Never saw the point. And I think I was emotionally immature too. The others all seemed so much more savvy! Although interestingly one of the studies states that girl's emotional development is linked to age; boys is directly affected my hormones. Though I'm sure puberty has some sort of impact.
I also developed hypothyroidism at around 18, but it wasn't diagnosed for some time and then not well controlled till my mid 20s. I've often wondered if that further impacted things at the time. It's certainly left me with a type of trauma linked to that time. (I became very weak and unable to do much, anxious, confused, depressed, studies were affected, friends were lost etc.)
What concerns me is that lupron has been known to permanently affect the thyroid system too in girls with precocious puberty. Low thyroid hormones do affect cognition. Lack of enough in the womb and maternal iodine deficiency and while growing up used to cause cretinism. This was eliminated when the dairy industry started to use iodine to sterilise udders.