In the circulation 99% of T3 is reversibly bound to transport proteins, primarily to thyroxine-binding globulin (TBG) and some to albumin. Free T3 does not bind to transport proteins but is free in the circulation and metabolically active or available. Its measurement correlates to total T3 secretion and metabolism. Both T3 and T4 affect most cells in the body by increasing basal metabolic rate and regulating carbohydrate, fat and protein metabolism.
Please refer to clinical details on TSH to review overall causes of thyroid disorders.
Test Results
| Raised TSH, low T4 | Hypothyroidism |
| Raised TSH, normal T4 | Consistent with subclinical hypothyroidism |
| Raised TSH, raised T4 | Thyroid hormone resistance, rarely TSH tumour. |
| Low TSH, raised T3 or T4 | Hyperthyroidism |
| Low TSH, normal T3, T4 | Subclinical hyperthyroidism |
| Low TSH, low T3 and T4 | Sick euthyroid disease, or pituitary disease. |
Please contact us for more information on the reference ranges used at Enfer Medical.
