I'm Thin: Could I Still Be Hypothyroid?

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Imagine this scenario. 

A woman has many symptoms of an underactive thyroid, but there's one major exception: she's slender and hasn't gained a pound. In some cases, she may have even lost weight. 

Yet she has other symptoms that point to an underactive thyroid. But she questions her own judgment, thinking that weight gain must be present with hypothyroidism, and assumes that her symptoms are caused by something else other than a thyroid problem. She may not even pursue an evaluation and diagnosis with her doctor. It's true that some doctors, too, can make the assumption that being "thin," rules out an underactive thyroid.

The bottom line is that a weight increase is simply one symptom of hypothyroidism. But it's not a hard and fast rule, meaning not everyone will report weight gain when they are diagnosed with hypothyroidism. 

Weight Changes and Other Symptoms of Hypothyroidism

Weight gain (or an inability to lose weight despite diet and exercise) in hypothyroidism is due to a slowing down of metabolic processes.

This symptom is supported by science too, as studies reveal there is a positive link between body mass index (BMI) and thyroid-stimulating hormone (TSH)—remember, TSH is increased in hypothyroidism. 

But there may be one or more (or none) symptoms and signs of a "slowed down" metabolism in hypothyroidism, besides weight gain, including:

  • Fatigue, unusual exhaustion, and weakness
  • Feeling cold, especially in the extremities
  • Shortness of breath upon exertion
  • Constipation
  • Difficulty concentrating, memory issues, brain fog
  • Slowness when moving or talking
  • Slow heart rate
  • Slowed reflexes

Besides the ones mentioned above, other potential symptoms and signs of an underactive thyroid include: 

  • Depression 
  • Dry, coarse and/or itchy skin
  • Hoarseness
  • Swelling (called edema)
  • Muscle cramps, aches/pain
  • Menstrual changes
  • Puffy face, puffiness around the eyes, and loss of eyebrows

In the end, if you are experiencing any symptoms of hypothyroidism, be sure to see your physician for a complete evaluation of your thyroid—and do not rely on any one issue (like your weight) to change your mind.

A Word From Verywell

The big picture here is that the symptoms of hypothyroidism are quite variable and nonspecific, meaning they could very well be due to another medical condition, or even a result of a new lifestyle change.

This is why there is only way to know if you (or a loved one) is hypothyroid—see a doctor and undergo a blood test for thyroid stimulating hormone (TSH). 

View Article Sources
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  • Braverman, L, Cooper D. Werner & Ingbar's The Thyroid, 10th Edition. WLL/Wolters Kluwer; 2012.
  • Garber JR et al. Clinical practice guidelines for hypothyroidism in adults: cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association. Endocr Pract. 2012 Nov-Dec;18(6):988-1028.
  • Solanki A, Bansal S, Jindal S, Saxena V, Shukla US. Relationship of serum thyroid stimulating hormone with body mass index in healthy adults. Indian J Endocrinol Metab. 2013 Oct;17(Suppl1):S167-69.