“Does Hashimoto's cause weight gain?”

Hashimotos that ends up as hypothyroidism can cause weight gain. This is also the reason why patients should be on replacement medications right away.

Yes

Hashimoto's disease is an auto-immune disease that is caused by your inheritance. The immune system can destroy the thyroid gland resulting in a hypothyroid state. Hypothyroid problems result in poor function of all organs, including the kidney. The kidney maintains water balance so if it is not working well there is fluid retension that can be manifested by weight gain. If you have Hashimoto's disease be sure to take your thyroid replacement daily and see the Dr. often to get the thyroid level checked & kept in control. Now though there are many other causes of wt. gain so see your Dr. to be sure the wt. gain does not have another cause and can be fixed.