I did have a definitive increase in my breast size post-thyroidectomy. As a matter of fact, that was how I ended up working at the Breast Care Center. I was going for monthly appointments because of how I was growing and I found out that they were seeking an office manager. Anyways, I'm getting off topic.
TBH, after my first mammogram and ultrasound, they had told me that there was no sign of cancer, I stopped worrying about the growth. I did continue with ultrasound follow-up appointments and eventually, things evened out and my breast growth stabilized. Within a year, I had gone from a 38E to a 38G. Since then, I lost about 40 pounds and most of my bras are a 36H UK sizing. I wear mostly UK bras because they tend to have a broader underwire that works very nicely with my breast shape. OMG 😲 I'm off topic again!!!! Lol 😆
My advice would be to make an appointment with your PCP to monitor any changes as a result of your surgery. You will likely be followed by an endocrinologist and possibly be referred to either a breast care center or a women's clinic to monitor your breasts and their potential growth.
♥️Sophie♥️