Penis shaft diameter changes

[Graybeard3]

I'm a 62yo male. In the last year or so I've noticed that the top third of my penis is noticeably thicker than the bottom third when fully erect. Well, noticeable to me--I tried to measure the difference and couldn't, but I can feel it. I'm sure this is new--let's face it, if there's one part of the body us guys know the exact topology of, that's it! There's no apparent problem: no tenderness, no dysfunction. Just seems...odd. A bunch of Googling hasn't found much other than the usual scam sites talking about enlargement methods.

Is this common? Rare but normal? Some mild form of Peyronie's disease? I have a great doctor and could ask her, but since it doesn't seem to be a problem--and I'm sure not going to be able to show her, since it only manifests when fully erect--that doesn't seem like a very useful avenue.

Thanks for any thoughts.