Thyroid Stimulating Hormone
- Sample Type
- Serum
- Fasting
- No
- Unit
- mIU/L
Function
Thyroid Stimulating Hormone (TSH), also known as thyrotropin, is produced by the anterior pituitary gland. Its primary role is to regulate the production of hormones (T3 and T4) by the thyroid gland. The system operates on a negative feedback loop: when thyroid hormone levels drop, the pituitary releases more TSH to 'stimulate' the thyroid. Conversely, when thyroid hormones are high, TSH production is suppressed.
Why it is Ordered
TSH is the gold-standard screening test for thyroid dysfunction. It is ordered to:
- Diagnose hypothyroidism (underactive thyroid) or hyperthyroidism (overactive thyroid).
- Screen newborns for congenital hypothyroidism.
- Monitor the effectiveness of thyroid hormone replacement therapy (e.g., Levothyroxine).
- Evaluate pituitary gland function.
Associated Conditions
- Hypothyroidism: Characterized by high TSH. Symptoms include fatigue, weight gain, and cold intolerance.
- Hyperthyroidism: Characterized by low TSH. Symptoms include anxiety, weight loss, and heat intolerance.
- Hashimoto's Thyroiditis: An autoimmune condition causing chronic hypothyroidism.
- Graves' Disease: An autoimmune condition causing hyperthyroidism.
Check Your Result
Check Your Result
Enter your lab result to see where you stand compared to the standard reference range.
Why Context Matters
TSH levels exhibit a diurnal rhythm, typically peaking at night and reaching their lowest point in the late afternoon. Biotin (Vitamin B7) supplements are a major confounding factor; high doses of biotin can cause falsely low TSH results (mimicking hyperthyroidism) in many lab assays. Additionally, 'Sick Euthyroid Syndrome' can occur during acute severe illness, where TSH levels become abnormal despite the absence of primary thyroid disease, often requiring a follow-up test after recovery.
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:
Official Sources
- TSH test: MedlinePlus Medical EncyclopediaMedlinePlus
Research & Guidelines
Related Indicators
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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