In a series of tweets, the 22-year-old catwalk star said she would not offer any more explanations to people on how her "body has matured".
"For those of you so determined to come up with why my body has changed over the years, you may not know that when I started at 17 I was not yet diagnosed with Hashimoto's disease; those of you who called me 'too big for the industry' were seeing inflammation and water retention due to that...
She said, "drugs are not my thing" and the people should stop labelling her as an addict as they do not understand her condition.
The model said that she has been under medication for the last few years and was also a part of a holistic medical trial that helped her thyroid levels balance out.
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"(I) am still learning and growing with my body everyday, as everyone is," she added.
Hadid requested social media users to learn to empathise with others and "know that you never really know the whole story".
"I think it's good to be honest. I've talked about my experience with Hashimoto's but a lot of people can connect with it. I've loved my body when I was just diagnosed and I loved (it) going through it and I love my body now...
"It's just about everyone accepting their body as it matures and knowing that it's not always going to look the same and you can love yourself in all different sizes," Hadid said.