Hypothyroidism can happen at any time, for a huge number of reasons. If there is a genetic concern and you were assessed at 13, you most likely won't have the juvenile form of this.
However, hypothyroidism can occur later in life due to autoimmune reactions (Hashimoto's), pregnancy, or as a side-effect of other medications or simply as a function of aging (like, over the age of 65 years old).
If you suspect you may be hypothyroid, you need to see a doctor for testing -- it is fairly simple and if there is a family history, you might want to get checked out because this is clearly on your mind.
Here's a good link for you on hypothyroidism:
PLEASE keep in mind that hypothyroidism needs to be treated, because if NOT, the symptoms WILL progress --
If hypothyroidism isn't treated, the symptoms will progress and, rarely, a severe form of hypothyroidism called myxedema will develop. With myxedema, the body temperature drops, anemia occurs, and there is a risk of congestive heart failure.
As the symptoms of hypothyroidism include weight gain, it will be hard to lose excess pounds if you have hypothyroidism which isn't treated. Here is another link on how to lose weight with hypothyroidism that is under treatment:
I'm just speaking off the top of my head here, but it seems to me that you have a family history of hypothyroidism, are currently experiencing difficulty losing weight, and may be concerned that your difficulty in losing weight might be an indication that you have developed hypothyroidism ---
Get thee to a doctor!!!!! Just get it checked out. The worst that can happen is that you will have the disease, get treated for it, and will become healthy and happy for a long time to come!!! Please see a doctor...
Let us know!