Thyroid Stimulating Hormone (TSH)

A diagnostic blood test measuring TSH levels to screen for thyroid dysfunction, including hypothyroidism (underactive) and hyperthyroidism (overactive).

Clinical Confidence

Verified by Dr. Narayan Jethwani, MD (Hom)

Flagship

Quick Reference Facts

Specimen TypeVenous Blood (Serum)
PreparationFasting optional; early morning draw is preferred
Turnaround Time12–24 Hours
Clinical CategoryEndocrine Screen

Evidence Summary

Body SystemEndocrine
Typical PrevalenceStandard endocrine biomarker
Typical Age RangeAll age groups
Clinical Urgencyroutine
Primary Etiological Factors
  • Primary thyroid gland failure (elevated TSH)
  • Pituitary adenoma or central failure (suppressed/low TSH)
Recommended Screenings
Free T4Free T3Anti-TPO Autoantibodies
High-Yield Clinical Pearl

"TSH fluctuates diurnally, peaking overnight. A borderline elevation should always be confirmed with an early morning repeat specimen."

Visual Body System Card

Affected SystemEndocrine
Organs Involved
Pituitary GlandThyroid Gland
Hormones Involved
TSHTRHT4T3

TSH Laboratory Reference Ranges & Clinical Interpretation

SuppressedOptimal RangeSubclinical HypoOvert Hypo0.00.452.5 (Target)4.510.0mIU/LTSH Spectrum (mIU/L)

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

Stage 1 of 5

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

TSH (Thyroid Stimulating Hormone, the master regulator of metabolic rate): A specialized laboratory marker or endocrine hormone measurement used to evaluate thyroid gland function, metabolic control, and autoimmune thyroid activity.

Standard Reference Range

TSH: 0.45 - 4.5 uIU/mL; Free T4: 0.8 - 1.8 ng/dL; Free T3: 2.3 - 4.2 pg/mL; Anti-TPO: < 9.0 IU/mL.

Elevated (High) Values

  • Primary hypothyroidism (elevated TSH)
  • Thyrotoxicosis or Graves' disease (elevated Free T4/T3)
  • Active autoimmune thyroiditis (elevated Anti-TPO / Anti-Tg)

Decreased (Low) Values

  • Hyperthyroidism or secondary hypothyroidism (low TSH)
  • Overt hypothyroidism (low Free T4/T3)
  • Non-thyroidal illness syndrome

Clinical Alignment & Significance

TSH evaluation: Elevated TSH with low Free T4 indicates primary hypothyroidism. Conversely, low TSH with high Free T4/T3 confirms hyperthyroidism. Elevated Anti-TPO indicates autoimmune thyroid disease.

Clinician TSH Interpretation Flowchart

Diagnostic Action

Measure initial serum TSH level

Decision Point

Is TSH level elevated (> 4.5 mIU/L)?

YesEvaluate Free T4NoCheck for low TSH (< 0.4 mIU/L)
Diagnostic Action

Measure Free T4 level

Decision Point

Is Free T4 level decreased?

YesConfirm Primary HypothyroidismNoSubclinical Hypothyroidism
Clinical Consideration

Screen for Anti-TPO autoantibodies to evaluate for autoimmune etiology (Hashimoto's)

Clinical Consideration

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.

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).

AI & Generative Search Citation Block

Entity IDL0002
Entity Typelab-test
Content Versionv1.0.0
Last Reviewed DateJun 30, 2026
Evidence LevelLevel-A
Suggested Academic/LLM Citation format (AMA Style)

Dr. Narayan Jethwani. "Thyroid Stimulating Hormone (TSH)." Homeo Healthcare Clinical Platform. Version 1.0.0. Reviewed: 2026-06-30T12:00:00Z. Available at: https://homeo.healthcare/knowledge/lab-tests/tsh

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