Thyroid-Stimulating Hormone (TSH) icon

Thyroid-Stimulating Hormone (TSH)

Content Source: Health3 AG
Data Compiled From: Clinical laboratory standards & peer-reviewed research
Quality Assurance: Verified against multiple authoritative sources
Academic Sources: Vestergaard, 2003; Zimmermann, 2002; Zhang, 2020; Hershman, 2023; Garber, 2012; Bauer, 2008; Koulouri, 2013; Mullur, 2014; Rifai, 2023; Ross, 2016; Duyff, 2000; Koulouri, 2013; Hage, 2012; Ylli, 2021; Ross, 2016; Garber, 2012; Zimmermann, 2009; Zimmermann, 2002; Garber, 2012; Ross, 2016; Green, 2021; Zhang, 2020; Harjai, 1997; Lazarus, 2009
Last Verified: 2025-12-09
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What is Thyroid-Stimulating Hormone (TSH)?

TSH is a hormone made by your pituitary gland (in the brain). It tells your thyroid to make thyroid hormones (T4 and T3). When T4/T3 are low, TSH usually goes up; when T4/T3 are high, TSH usually goes down. This ""feedback loop"" helps keep your body in balance. TSH affects many body systems because it controls thyroid hormone levels, which influence energy use, heart rhythm, body temperature, mood, and thinking.[Mullur, 2014]

Low TSH (often signals an overactive thyroid)

Low TSH commonly happens when the thyroid is overactive (hyperthyroidism) or when too much thyroid medicine is taken. People may notice a fast or irregular heartbeat, nervousness, heat intolerance, and weight loss. Lower TSH with higher thyroid hormone levels is linked with a higher risk of atrial fibrillation (irregular heartbeat).

High TSH (often signals an underactive thyroid)

High TSH usually means the thyroid is underactive (hypothyroidism). Symptoms can include tiredness, feeling cold, weight gain, dry skin, and constipation. Hypothyroidism can also affect mood and thinking; treatment helps, but some symptoms may take time to improve.

To maintain healthy TSH levels

  • Get enough iodine (iodized salt or foods as advised). Iodine is required to make thyroid hormones.[Zimmermann, 2009]
  • Keep iron status healthy; low iron can impair thyroid hormone production.[Zimmermann & Kohrle, 2002]
  • Ensure selenium intake is adequate; selenium‑dependent enzymes help activate/inactivate thyroid hormones.[Zimmermann & Kohrle, 2002]
  • Tell your clinician about biotin supplements (often in ""hair/nails"" products). Biotin can distort lab results (often making TSH look falsely low). Stopping biotin before testing is often advised; follow your lab/clinician''s guidance.[Zhang, 2020]
  • Some medicines (e.g., amiodarone, lithium) can affect thyroid function; monitoring may be needed.[Harjai, 1997][Lazarus, 2009]

Measurement Units

Thyroid-Stimulating Hormone (TSH) can be measured in: mIU/L, µIU/mL

Reference Ranges by Age and Gender

Reference ranges represent typical values for healthy individuals. Your healthcare provider must interpret your specific results.

Age Range Gender Unit Optimal Normal Source
21 - 54 All genders mIU/L - 0.4 - 4.2 Rifai, 2023
55 - 87 All genders mIU/L - 0.5 - 8.9 Rifai, 2023

Health Impact

Muscle Function​

TSH is your thyroid''s control signal: high TSH usually means low thyroid hormone and is linked with heavy, cramp-prone, weak muscles. Low TSH often signals high thyroid hormone and can show up as tremor, shakiness, and muscle wasting.[Duyff, 2000][Garber, 2012][Ross, 2016]

Mood Regulation​

High TSH (low hormones) is linked with low mood, low energy, and ""brain fog."" Low TSH (high hormones) can present as anxiety, irritability, and restlessness—restoring normal thyroid often improves mood.[Garber, 2012][Hage, 2012][Ross, 2016]

Sleep Quality​

Low TSH (high hormones) is linked with insomnia, restlessness, and palpitations. High TSH (low hormones) is linked with excess sleepiness and low energy—fixing the thyroid often improves sleep.[Ross, 2016][Garber, 2012][Green, 2021]

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Academic References

  1. Vestergaard P and Mosekilde L. Hyperthyroidism, bone mineral, and fracture risk—a meta-analysis (2003). Thyroid. View Source
  2. Zimmermann MB and Köhrle J. The impact of iron and selenium deficiencies on iodine and thyroid metabolism (2002). Thyroid. View Source
  3. Zhang Y. Assessment of biotin interference in thyroid function tests (2020). Medicine (Baltimore). View Source
  4. Hershman JM. Thyroid Function Tests (2023). Clinical Resource.
  5. Garber JR. Clinical practice guidelines for hypothyroidism in adults (2012). Endocr Pract. View Source
  6. Bauer M. The thyroid-brain interaction in thyroid disorders and mood disorders (2008). J Neuroendocrinol. View Source
  7. Koulouri O. How to interpret thyroid function tests (binding effects) (2013). Clin Med (Lond). View Source
  8. Mullur R, Liu YY, and Brent GA. Thyroid hormone regulation of metabolism (2014). Physiol Rev. View Source
  9. Rifai N.. Tietz Textbook of Laboratory Medicine (2023). Elsevier.
  10. Ross DS. 2016 American Thyroid Association guidelines (2016). Thyroid. View Source
  11. Duyff RF. Neuromuscular findings in thyroid dysfunction (2000). J Neurol Neurosurg Psychiatry. View Source
  12. Koulouri O. How to interpret thyroid function tests (binding effects) (2013). Clin Med (Lond). View Source
  13. Hage MP and Azar ST. The link between thyroid function and depression (2012). J Thyroid Res. View Source
  14. Ylli D. Biotin Interference in Assays for Thyroid Hormones, Thyrotropin and Thyroglobulin (2021). Thyroid. View Source
  15. Ross DS. 2016 American Thyroid Association guidelines (2016). Thyroid. View Source
  16. Garber JR. Clinical practice guidelines for hypothyroidism in adults (2012). Endocr Pract. View Source
  17. Zimmermann MB. Iodine deficiency (2009). Endocr Rev. View Source
  18. Zimmermann MB and Köhrle J. The impact of iron and selenium deficiencies on iodine and thyroid metabolism (2002). Thyroid. View Source
  19. Garber JR. Clinical practice guidelines for hypothyroidism in adults (2012). Endocr Pract. View Source
  20. Ross DS. 2016 American Thyroid Association guidelines (2016). Thyroid. View Source
  21. Green ME and Bernet VJ. Thyroid dysfunction and sleep disorders (2021). Front Endocrinol (Lausanne). View Source
  22. Zhang Y. Assessment of biotin interference in thyroid function tests (2020). Medicine (Baltimore). View Source
  23. Harjai KJ and Licata AA. Effects of amiodarone on thyroid (1997). Ann Intern Med. View Source
  24. Lazarus JH. Lithium and thyroid: clinical aspects (2009). Best Pract Res Clin Endocrinol Metab. View Source

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