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Hyperthyroidism without triiodothyronine excess: an effect of severe non-thyroidal illness
The Journal of Clinical Endocrinology and Metabolism
|January 1, 1978
Summary
Transient non-thyroidal illness can alter thyroid hormone levels in hyperthyroid patients. Changes in triiodothyronine (T3) and reverse T3 (rT3) may complicate diagnosis, highlighting the need for careful interpretation of thyroid function tests.
Area of Science:
- Endocrinology
- Internal Medicine
Background:
- Hyperthyroidism is a condition characterized by excessive thyroid hormone production.
- Non-thyroidal illness (NTI) can significantly impact thyroid hormone metabolism.
- Understanding thyroid hormone dynamics during NTI in hyperthyroid patients is crucial for accurate diagnosis and management.
Observation:
- Two hyperthyroid patients experienced transient NTI (cholecystitis and undiagnosed illness with fever).
- Serial thyroid hormone measurements revealed altered levels of triiodothyronine (T3) and reverse T3 (rT3).
- Thyroid-stimulating hormone (TSH) response to thyrotropin-releasing hormone (TRH) was undetectable in one patient.
Findings:
- Subnormal T3 and elevated rT3 concentrations were observed during NTI episodes in hyperthyroid patients.
- T3 levels normalized, and rT3 decreased during recovery.
- In one case, hyperthyroidism evolved from a T3 toxicosis state to classical hyperthyroidism after NTI resolution.
Implications:
- The study demonstrates that typical NTI-induced thyroid hormone changes also occur in hyperthyroid individuals.
- Reduced T3 levels during NTI may render T3 measurements unreliable for diagnosing hyperthyroidism.
- These findings underscore the importance of considering NTI when interpreting thyroid function tests in hyperthyroid patients.