Normal Reference Ranges
Adult
0.4 - 4.0 mIU/L
Pediatric
0.5 - 5.0 (varies by age) mIU/L
Clinical Significance
Best initial test for evaluating thyroid function. Regulates the synthesis and release of thyroid hormones.
Causes of High
- Primary Hypothyroidism (Hashimoto's)
- TSH-secreting pituitary tumor
- Inadequate thyroid hormone replacement
Causes of Low
- Primary Hyperthyroidism (Graves')
- Excessive thyroid hormone replacement
- Severe non-thyroidal illness