Thyroid and Weight Gain: Sorting Fact from Myth
The thyroid gets blamed for a lot. Sometimes it is the culprit; often it is not. Here is how to tell.
How the thyroid affects weight
Overt hypothyroidism (TSH > 10, low free T4) reduces basal metabolic rate by 10–20% and typically causes a 2–5 kg weight gain, most of it fluid. Correcting the hypothyroidism restores metabolic rate but rarely produces dramatic weight loss on its own.
The subclinical grey zone
A TSH between 4.5 and 10 with normal free T4 is subclinical hypothyroidism. Whether to treat depends on symptoms, antibody status (TPO), age, and cardiovascular risk. Many symptomatic patients benefit from a trial of levothyroxine — but this is a shared decision, not automatic.
Get your thyroid checked
Ready to take the next step? Book a weight management initial consultation at CurAge Santé, or explore all options on our Weight Management services page.
Frequently asked questions
Should I request T3 and reverse T3?+
Only in specific clinical contexts. TSH and free T4 answer most questions correctly.