I see. While side effects like the one you experience (glans sensitivity loss) are not listed for the medication you take, one cannot rule this out completely, even if it happens after years of treatment. It is probably a combination of drugs and the after-circumcision effects that may take many years before showing up.
The problem with your frenulum makes me wonder in what condition your skin is generally. Do you take enough zinc daily? Adults need around 15 mg of zinc everyday for many vital functions, good skin health being one of them. If not, you may consider a zinc supplement but as you still take drugs, don't forget to ask your doctor before.
Thanks for your response. I have been and continue to be tested for MS - although I am still awaiting a definite diagnosis, despite already having an MRI scan which was inconclusive. I take a variety of drugs for my neurological symptoms, including Tramadol, Gabapentin and Amitryptiline and while combined they do have a profound effect (making me drowsy, etc.), I have been taken this combination of drugs for several years and have only recently started to experience the loss of sensation in my penis.
I still have a frenulum and while this does have some sensation, I have experienced a dramatic loss of feeling in the frenulum, ever since the onset of the loss of sensation in my glans.
One thing that may be of significance is that I have, today, noticed a small tear in the underside of the frenulum, which although not bleeding or painful, is quite worrying.
As you said, circumcision played a major role in what you experience right now. However, your neurological problems would make me think that you took (still take?) medication for this. There is probably some interaction between the treatment and the glans sensitivity. But this is something you should look at with the assistance of your doctor.
Another point: do you still have your frenulum? Does it responds to stimulation?