Normal Thyroid Physiology
Laboratory Tests for Thyroid
| Total T4 | Free T4 | Total T3 | TSH | |
|---|---|---|---|---|
| Normal |
4.5 – 12.5 mcg/dl |
0.8 - 1.5 ng / dl |
80 – 220 ng/dl |
0.3 – µU / mL |
| Hyperthyroid |
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| Hypothyroid |
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Thyroid Clinical Pearls
- Normal levothyroxine dose is 1.6 mcg/kg/ day
- Some people may benefit symptomatically from addition of 50mcg of T3 to levothyroxine
- Normal TSH should probably not be above 3.5 Treated
- Untreated TSH should be between 0.5 to 3.8 mU/L
- 100 and 300 mcg tabs have yellow dye #5 and have allergic potential
Amidarone induced hypothyroidism: 2 mechanisms :
- Thyroiditis: use a steroid
- Iodine induced: use Synthroid
Subclinical hyperthyroidism consequences:
- Osteoporosis mostly in post-menopausal women
- A. Fib. 3 fold increase in risk
- Increase LV mass (diastolic dysfunction)