Symptoms of Low Thyroid Stimulating Hormone

Low thyroid stimulating hormone (TSH) levels suggest hyperthyroidism (overactive thyroid).

A variety of conditions lead to hyperthyroidism, including Graves' disease and thyroid nodules. A little over 1% of adults in the United States have hyperthyroidism.

This article discusses the symptoms of low TSH.

Getting blood drawn

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Frequent Symptoms of Low TSH

Though TSH levels are important measures of thyroid function, low TSH levels do not always cause symptoms. However, low levels of TSH are associated with hyperthyroidism, which can cause:

  • Irritability
  • Feeling tired
  • Muscle weakness
  • Trouble tolerating heat
  • Difficulty sleeping
  • Tremors
  • Rapid and irregular heartbeat
  • Diarrhea
  • Weight loss
  • Mood swings

Pregnancy Concerns

Mild hyperthyroidism while pregnant does not always cause problems. Moderate-to-severe hyperthyroidism can lead to various complications. 

  • For the baby: Uncontrolled or untreated hyperthyroidism of the mother during pregnancy is associated with a baby size that is small for gestational age, preterm birth, stillbirth, and possibly congenital malformations. 
  • For the mother: Potential complications of untreated hyperthyroidism include preeclampsia and, rarely, thyroid storm

Though uncommon, hyperthyroidism may also occur in mothers of newborns with a history of treated Graves' disease (meaning their disease is in remission). This is why it's important to notify your healthcare provider of any history of thyroid disease in addition to active thyroid disease.

Rare Symptoms

Although less common, some rare symptoms of low TSH levels linked to hyperthyroidism include: 

  • Heart arrhythmias such as atrial fibrillation
  • High fever 
  • Mental status changes

Other Symptoms to Look Out For

Other medical problems, like anemia (a decrease in red blood cells), can also indicate that someone has low TSH and hyperthyroidism.


Low TSH levels are an indicator of abnormal thyroid function and should be corrected.

The thyroid plays a central role in numerous body processes, such as energy, metabolism, skin health, mood, and heart function. Over the long term, low TSH levels can potentially lead to damage to major organ systems, so they should not be dismissed. Serious complications include:

When to See a Healthcare Provider

A low TSH level is not often a medical emergency. If you have blood work that illustrates a low TSH level, talk with your healthcare provider about the potential causes and the next steps for diagnosis and treatment.

Fortunately, there are numerous treatments available for low TSH levels, including medications and procedures. If you are experiencing any severe symptoms, such as high fever, palpitations, or changes in thinking or memory, then seek care immediately. 


A low TSH level is linked to thyroid hormone levels in the body and is a common condition. In some cases, increased levels of thyroid hormone caused by supplementation or conditions such as Graves' disease can contribute to a low TSH. 

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. University of Michigan Health. Hyperthyroidism and Graves' disease.

  2. MedlinePlus. Hyperthyroidism.

  3. American Thyroid Association. Hyperthyroidism in pregnancy.

  4. Rajendran A, Bhavani N, Nair V, et al. Oral levothyroxine is an effective option for myxedema coma: a single-centre experience. Eur Thyroid J. Published online June 11, 2020:1-7. doi:10.11592F000507855

  5. Wilson SA, Stem LA, Bruehlman RD. Hypothyroidism: diagnosis and treatment. Am Fam Physician. 2021;103(10):605-613.

  6. National Institute of Diabetes and Digestive and Kidney Diseases. Hyperthyroidism (overactive thyroid).

By Kevin James Cyr
Kevin is a physician-in-training at Stanford University School of Medicine with a focus in cardiovascular disease and bioengineering. His publications have earned international awards, and his work has been featured in major media outlets such as NBC News.