Review Article
The Use of TSH in Determining Thyroid Disease: How Does It Impact the Practice of Medicine in Pregnancy?
Table 1
Clinical situations in which measurements of serum TSH alone may yield misleading results.
| Condition | Serum TSH | Consequences of Clinical Action based on Serum TSH value Alone | Serum FT4 |
| Heterophile antibodies | Normal | Failure to diagnose thyrotoxicosis | High | Central hypothyroidism | Normal* | Failure to diagnose hypothyroidism and investigate hypothalamic-pituitary structure function | Low | TSH-secreting pituitary adenoma | Normal* | Failure to diagnose thyrotoxicosis and investigate pituitary structure and function | High | Thyroid hormone resistance | Normal* | Failure to recognize the condition | High | Poor compliance with T4 therapy | High | Inappropriate increase in dose of T4 | High | Delayed recovery of TSH secretion after treatment of hyperthyroidism | Normal or low | Failure to diagnose impending hypothyroidism | Low |
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Serum TSH concentrations may also be high in these conditions, which should prompt measurements of serum FT4 and further investigation.
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