I have Graves Disease. I went for about a year without treatment because I didn't know anything was wrong. Could the hyperT have caused my feet to grow? I've always had big feet for a woman (size 11). I was trying on shoes at the store, and they were all too tight! Had to buy men's shoes.
I would suspect swelling is causing you to need larger shoes, not growth. Look for a place that sells women's shoes in wide widths. Most are B width for women, D width for men. You have probably been wearing Bs for most of your life and now need a C or D. If there is no store offering different widths in your town you can get them on line.
I never say never, but I doubt foot size has anything to do with thyroid.
I also have always had large feet, and if you feel like I do about that, I know you won't like this information... but... feet continue to grow throughout adulthood, just at a slower rate. My feet have grown two half-sizes since I was in my late 30's, from a 10 to now an 11 in my late 50's. My husband's feet have also gained length during his adult lifetime, from a size 12 to his current 14. My son's feet - he's 33 - have grown in the past few years, since he gained considerable weight.
An increase in foot size can occur for several reasons: Adaptation to weight gain and loss, muscular imbalance and pregnancy can permanently change foot size. This is due to changes in the ligaments, tendons, and muscles within the foot, followed by subtle changes in the joints and spreading of the bones. The result is a normal enlargement of the foot which may be so gradual that sometimes it goes unnoticed. Individuals who spend all day on their feet, people who exercise, and women during and after pregnancy are especially susceptible.
Like you say, never say never, but with fewer and fewer quality shoe retailers around most adults who find they need wider shoes are forced to buy longer ones because most stores carry only D widths for men and B widths for women. Widths, of course, grow proportionately as size/length increases.
Proper sizing is determined by the distance from your heel to the bulging big toe joint (not to the end of the toes). Widths are determined by the relationship between actual width at the widest point (again, at the big toe joint) compared to length-size. If you find you are needing larger shoes as you age suspect, first, that your feet are getting fatter and wider, or swollen and wider. The distance between the end of the heel to the big toe joint rarely changes once you've reached maturity. If it does change I would suspect too much growth hormone or acromeglia (sp?).
Archie, you're so wise in so many ways that I would agree with you if I didn't know differently.
I wore the same brand and style of athletic walking shoe for at least 17 years. I started out with a size 10B. Over the course of time, my big toe started bumping the end of the shoe with each step. Because women's shoes are incredibly hard to find in size 10 1/2, I tried a 10W. It didn't work. My toe still bumped, and the extra width provided no support to my heel and middle foot. By a stroke of luck, I was able to locat a retailer that carried that exact shoe in a 10 1/2B. That was the size I needed, so I was all set for another 6 years or so.
Repeat story... except to say that size 11 is much easier to find. I now wear that very same shoe in an 11B. The width has not changed; only the length has.
I'm living proof that length can increase with age as well as width.
My husband has had the same experience, having worn the same manufacturer's work boots for decades. He wore a 12D in his youth; he wears a 13D now in that brand. In another manufacturer's athletic style, he has gone from a 13D to a 14D within the past five years. Again, change in length, not width.
Now, I'm sure there are explanations other than the bones put on more growth. Tendons and ligaments loosen with age... lord don't I know that!... and so spread probably occurs just as often in length as width. I just happen to believe that it occurs to everyone, regardless of thyroid status.
It isn't unusual for a grown adults feet to grow. It happened to me (went from size 8 to size 9) and it had nothing to do with swelling feet. I mentioned this to my doctor and he told me his feet grew a size also (we are the same age and it happened about 15 years ago).
I think it had to do with being on my feet a lot after a job change. Could this be the case with you?
If you had high arches when young it is certainly possible that they have sagged due to having to stand a lot in shoes that didn't provide adequate support. Sagging or settling of a high arch would move that big toe joint a little further away from the heel, increasing the measured size of your ideal shoe. An adult foot whose bones actually grow would be extremely rare and suggests a potentially serious medical issue, IMO.
BTW, I've worn the same 8Ds since my skeleton stopped growing, sometime around the age of 15 or so. That would be for 40 plus years. On my 6' 1" frame those size 8s make me very unstable in a strong wind.