Signs of Hyperthyroidism vs. Hypothyroidism: How to Tell the Difference

Both are thyroid diseases, but their symptoms are polar opposites.

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OK, so you feel tired all the time. Doesn’t everyone? Oh, and you always feel cold when others are comfortable. That’s normal … right? Sure, symptoms like these could be caused by the weather—but they could also be a sign of a thyroid problem.

The thyroid is a small, butterfly-shaped gland that lives at the base of your neck. It plays an important role in how your body functions. This gland secretes thyroid hormones which help control the way your body uses energy, including how fast your heart beats or how quickly you burn calories.

Disorders of the thyroid range in severity—from goiter (an enlarged thyroid gland) all the way to thyroid cancer. The most common thyroid problems involve abnormal production of the thyroid hormones, called hyperthyroidism and hypothyroidism.

Hyperthyroidism, or overactive thyroid, is when the thyroid gland produces too much thyroid hormone. High thyroid hormone levels can cause bodily functions to speed up, which may lead to these symptoms:

  • Nervousness
  • Irritability
  • Fatigue
  • Muscle weakness
  • Trouble tolerating heat
  • Trouble sleeping
  • Shaky hands
  • Fast heartbeat
  • Diarrhea
  • Weight loss
  • Mood swings
  • Or a swollen neck.

Hypothyroidism, or underactive thyroid, on the other hand, is when the thyroid produces too little hormone. This can cause bodily functions to slow down, which may cause symptoms such as:

  • Fatigue
  • Weight gain
  • Trouble tolerating cold
  • Constipation
  • Muscle weakness or pain
  • Dry skin or hair
  • Decreased sweating
  • Irregular periods
  • Slowed heart rate
  • Or a swollen neck or face.

If these conditions are left untreated, they can contribute to other health problems.

Hyperthyroidism can lead to:

  • An irregular heartbeat that can lead to heart-related problems such as: blood clots, stroke, or heart failure

  • Graves’ ophthalmopathy, which is an eye disease that can cause double vision, light sensitivity, eye pain, and rarely, vision loss

  • Or thinning bones and osteoporosis.

Hypothyroidism can contribute to high cholesterol, so people with high cholesterol should be tested for hypothyroidism to see if that is the underlying problem.

If you suspect you have hyperthyroidism or hypothyroidism, it’s important to see a doctor to get tested, and if diagnosed, treated. With the right treatment, you can get your thyroid levels back on track.