Thyroid Stimulating Hormone (TSH)
A diagnostic blood test measuring pituitary TSH levels to evaluate thyroid gland function, screening for primary hypothyroidism, hyperthyroidism, and subclinical thyroid disorders.
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Independent clinical validation is pending.
Article Editorial Timeline
Intelligent Context-Aware Learning Path
Objective: Assess Thyroid Stimulating Hormone status
2 min readPatient Protocols: Fasting and prep instructions
1 min readTSH: Regulates thyroid gland hormone release
5 min readHypothyroidism: Low thyroid hormone production
6 min readHair Fall: May occur in autoimmune thyroid disease
3 min readFT4: Measures circulating thyroid storage hormone
4 min readBook Consultation
Quick Reference Facts
Evidence Summary
- •Primary thyroid gland failure (elevated TSH)
- •Pituitary adenoma or central failure (suppressed/low TSH)
"TSH fluctuates diurnally, peaking overnight. A borderline elevation should always be confirmed with an early morning repeat specimen."
Visual Body System Card
TSH Laboratory Reference Ranges & Clinical Interpretation
Note: Standard diagnostic range for adults is typically 0.45 - 4.5 mIU/L. Values outside these boundaries warrant Free T4 evaluation.
Laboratory Interpretation Workflow
1. Clinical Indication
Ordering protocols based on clinical indications, presenting symptoms, or screening guidelines.
Clinical Pearl: Order when screening for primary organ dysfunctions or monitoring active treatment efficacy.
Test Description & Overview
Thyroid Stimulating Hormone (TSH (Thyroid Stimulating Hormone, the master regulator of metabolic rate), thyrotropin) is a pituitary glycoprotein hormone that regulates thyroid hormone (T4/T3) synthesis and secretion. Serum TSH (Thyroid Stimulating Hormone, the master regulator of metabolic rate) is the primary diagnostic screen for thyroid axis function due to the inverse log-linear relationship between TSH (Thyroid Stimulating Hormone, the master regulator of metabolic rate) and serum free T4.
Adult Non-Pregnant TSH: 0.45–4.50 mIU/L; First Trimester Pregnancy: 0.10–2.50 mIU/L; Free T4: 0.8–1.8 ng/dL; Free T3: 2.3–4.2 pg/mL.
Elevated (High) Values
- Primary Hypothyroidism (TSH > 4.5 mIU/L with low Free T4)
- Subclinical Hypothyroidism (TSH > 4.5 mIU/L with normal Free T4)
- TSH-secreting pituitary adenoma or thyroid hormone resistance (rare causes of high TSH with high Free T4)
Decreased (Low) Values
- Primary Hyperthyroidism / Thyrotoxicosis (TSH < 0.45 mIU/L with elevated Free T4/T3, e.g., Graves' disease, toxic nodular goiter)
- Subclinical Hyperthyroidism (TSH < 0.10 mIU/L with normal Free T4/T3)
- Central / Secondary Hypothyroidism (low or inappropriately normal TSH with low Free T4 due to pituitary failure)
Clinical Alignment & Significance
TSH is the initial screening biomarker. If TSH is abnormal, reflex Free T4 and thyroid autoantibodies (Anti-TPO, Anti-Thyroglobulin) delineate autoimmune etiology (Hashimoto's thyroiditis vs Graves' disease). Serum TSH fluctuations require morning repeat confirmation.
Clinician TSH Interpretation Flowchart
Measure initial serum TSH level
Is TSH level elevated (> 4.5 mIU/L)?
Measure Free T4 level
Is Free T4 level decreased?
Screen for Anti-TPO autoantibodies to evaluate for autoimmune etiology (Hashimoto's)
Correlate with clinical findings (hypometabolic symptoms, bradycardia) to guide care
Diagnostic Guidance Notice
Standard laboratory reference ranges vary based on the testing facility. Significant deviations require immediate clinician review to rule out severe medical pathology.
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Reference Citations & Evidence Sources
Clinical Guidelines & Consensus Statements
- CIT-0012Jonklaas J., Bianco A. C., Bauer A. J., et al.. "Guidelines for the Treatment of Hypothyroidism: Prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement." Thyroid (2014).DOI PubMed
- CIT-0013Garber J. R., Cobin R. H., Gharib H., et al.. "Clinical Practice Guidelines for Hypothyroidism in Adults: Cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association." Endocrine Practice (2012).DOI PubMed
- CIT-0014Demers L. M., Spencer C. A.. "Laboratory Medicine Practice Guidelines: Laboratory Support for the Diagnosis and Monitoring of Thyroid Disease." National Academy of Clinical Biochemistry (NACB) (2002).
Clinical Reviews & Textbooks
- CIT-0022Jethwani N.. "Internal Clinical Review Note: Standard Reference Values and Homeopathic Therapeutic Mappings for Lab Diagnostics." Homeo Healthcare Internal Review Series (2026).
AI & Generative Search Citation Block
L0002Dr. Narayan Jethwani. "Thyroid Stimulating Hormone (TSH)." Homeo Healthcare Clinical Platform. Version 1.1.0. Reviewed: 2026-07-30T12:00:00Z. Available at: https://homeo.healthcare/knowledge/lab-tests/tsh
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