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Even Slight Shifts in Thyroid TSH Level Associated with Weight Gain

Even Small Increases In Normal Range Linked to Weight Gain


Updated May 30, 2014

Woman weighing herself at home
Quiet Noise Creative/Digital Vision
While experts know that an overactive thyroid -- hyperthyroidism -- can cause weight loss, and a slower thyroid -- hypothyroidism -- can contribute to weight gain, they've pinpointed even more of a thyroid-weight connection with new research.

A study reported in the March 24, 2008 issue of the Archives of Internal Medicine looked at the connection between TSH levels and weight, and found that even slight increases in TSH within the normal range, over time, appear to be associated with weight gain.

Within the normal range of TSH -- which for the purposes of this study, used the wider range of 0.5 to 5.0 -- small increases in TSH were clearly associated with increases in body weight, according to the researchers.

The study authors summarized their findings:

"Thyroid function (as assessed by serum TSH concentration) within the reference range is associated with body weight in both sexes. Our findings raise the possibility that modest increases in serum TSH concentrations within the reference range may be associated with weight gain."
The researchers offered two possible reasons that might explain their findings.

First, lower energy expenditure -- known as thermogenesis -- is associated with lowered thyroid function.

Second, lower triiodothyronine (T3) levels are associated with lowered resting metabolic rates.

What Does this Mean For You?

Right now, the implications of these findings aren't clear, because while they've determined that increased TSH levels -- even within the normal range -- may play a role in weight gain, there is no definite cause and effect. It's not clear that lowering the TSH level -- for example, with thyroid hormone replacement therapy -- will reverse that finding and cause weight loss.

The main conclusion, therefore, is that while increases in TSH may be associated with weight gain, further research is needed to understand why, and whether this is preventable or treatable.

When You Need to Lose Weight

If you are overweight, and can't lose weight despite a healthy diet and exercise, you should have a full thyroid evaluation to rule out hypothyroidism. An underactive thyroid can sabotage even the best diet and exercise plans. To help learn more, take my quiz: Is Your Thyroid Making You Fat?

If you are overweight, and being treated for a thyroid problem, but finding it hard -- or impossible -- to lose weight, you'll want to learn about optimizing your thyroid treatment, and tactics thyroid patients can follow for effective weight loss. A great starting place is the Free 4 Weeks to Weight Loss Email Ecourse. You can sign up online now for this free course, delivered by email.

Finally, the Thyroid Diet and Weight Loss Information Center has dozens of articles, resources and tools to help thyroid patients lose weight.


Fox, Caroline S. et. al. "Relations of Thyroid Function to Body Weight: Cross-sectional and Longitudinal Observations in a Community-Based Sample," Archives of Internal Medicine. 2008;168:568-569, 587-592. Vol. 168 No. 6, March 24, 2008

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