Thyroid-Stimulating Hormone (TSH)
TSH is an anterior pituitary glycoprotein that regulates thyroid gland iodine uptake, thyroid hormone synthesis, and basal metabolic rate via negative feedback control.
Standard vs. Optimal Reference RangesμIU/mL
Standard reference intervals represent the statistical 95% distribution of unselected commercial populations. Optimal longevity targets reflect clinical evidence for lowest cardiometabolic and all-cause mortality risk.
Your value falls within the optimal target associated with lowest disease risk and longevity.
0.45 - 4.50 μIU/mL
General reference distribution across unselected commercial populations.
1.0 - 2.0 μIU/mL
Concentration target associated with minimal all-cause cardiometabolic mortality.
Molecular Mechanism & Clinical Purpose
Hypothalamic TRH stimulates pituitary TSH release, which binds the TSH G-protein coupled receptor on thyroid follicular cells to activate adenylate cyclase, stimulating thyroglobulin iodination and T4/T3 secretion.
Differential Diagnosis
Elevated Levels (TSH High)
- •Primary hypothyroidism (Hashimoto thyroiditis)
- •Subclinical hypothyroidism (2.5 - 10.0 μIU/mL with normal FT4)
- •Recovery phase from non-thyroidal illness
Low Levels (TSH Low)
- •Primary hyperthyroidism (Graves disease, toxic multinodular goiter)
- •Central hypothyroidism (pituitary adenoma/dysfunction)
- •Exogenous thyroid hormone overreplacement
Technical Reference & Deep Dive
Biochemistry & Enzymatic Pathways
Longevity Risk Architecture & Epidemiology
Pre-Analytical Caveats & Diagnostic Workup
Pre-Analytical Considerations:
Blood draw must occur strictly between 7:00 AM and 9:00 AM to account for steep circadian cortisol and testosterone peaks. Ensure 8 hours of restful sleep prior; night shift work or sleep deprivation severely blunts endocrine pulsatility. Discontinue biotin supplements for 72 hours before thyroid or steroid testing to prevent false immunoassay results. For reproductive hormones in premenopausal females, precisely document the day of the menstrual cycle (Day 3 for baseline follicular, Day 21 for luteal).
Reflexive Testing Protocol:
- Free Hormone Equilibrium Dialysis or LC-MS/MS assay for direct bioavailable hormone quantification
- Pituitary trophic hormone panel (TSH, LH, FSH, ACTH, Prolactin) to differentiate primary vs central secondary endocrinopathies
- Autoantibody quantification (Thyroid Peroxidase Antibodies, Thyroglobulin Antibodies, 21-Hydroxylase Antibodies)
- Pelvic, testicular, or thyroid high-resolution ultrasound imaging to assess glandular parenchymal architecture
- Dynamic endocrine stimulation testing (Cosyntropin/ACTH stimulation test, Dexamethasone suppression test, GnRH test)
Clinical Citations & Primary Literature (1)
- [1]Subclinical Thyroid Dysfunction and Cardiovascular Risk: A Meta-Analysis - JAMA (2021). PMID: 33755122
Associated Longevity Guides & Clinical Calculators
Medicine 3.0Explore comprehensive evidence-based clinical protocols, testing costs, and algorithmic calculators that incorporate Thyroid-Stimulating Hormone (TSH) into overall healthspan optimization.