Hello,
Get your thyroid function tests done because hypothyroidism results in weight gain.
Thanks

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Brief answer.....there can be many reasons for weight gain other than hypothyroidism.
Detailed answer...
Hello,
Thanks for the query.
Although underactive thyroid is one the most common cause of weight gain but there are other various reasons which can lead to weight gain and need to be looked into,like...
Too much stress 
Severe depression
Lack of sleep
Hormonal mess up in premenopausal state
Diseases of liver,kidney,heart etc where there is retention of water in the body.
Problems like ovarian tumours or cysts
Eating excess of fast foods ,junk foods and fried foods and total lack of activity
Consumption of medicines like anti depressants,birth control pills,steroids,some blood pressure and diabetes medicines etc

You should discuss about these above mentioned possibilities with your doctor and get examined and managed on those lines
I hope it helps,however you may revert to me for any further query.
Best of luck
Thanks

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