Endocrinology

Thyroid Stimulating Hormone (TSH)

Normal Range
0.40 - 4.50 mIU/L
Sample Type
Standard
Fasting
No
Unit
mIU/L

TSH, produced by the anterior pituitary, is the most sensitive marker for screening thyroid dysfunction. It operates via a negative feedback loop: when thyroid hormones (T3/T4) are low, TSH rises to stimulate the gland; when they are high, TSH drops. It is essential for diagnosing Hypothyroidism and Hyperthyroidism, and for titrating levothyroxine therapy.

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Interactive
mIU/L

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Why Context Matters

Biotin (Vitamin B7) supplements can cause analytically false low TSH results. Furthermore, 'Euthyroid Sick Syndrome' during acute systemic illness can cause abnormal TSH levels in patients with a healthy thyroid. Pregnancy-related HCG can also suppress TSH levels in the first trimester.

Lab ranges are statistical averages, not biological laws. "Normal" for a 20-year-old male isn't normal for a 60-year-old female.

Clinical References

Source-of-truth databases and clinical guidelines for Thyroid Stimulating Hormone (TSH):

Related Indicators

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Medically Reviewed by Dr. Binoy Babu, MBBS

Board Certified Doctor • 10+ Years Clinical Experience

Dr. Babu is a practicing physician dedicated to empowering patients with clear, actionable medical information. He founded 2opi to bridge the gap between complex lab reports and patient understanding, ensuring everyone has access to a reliable second opinion.

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