From the Guidelines
If you have high iron levels and elevated TSH after an iron infusion, you should consult your healthcare provider promptly for evaluation and consider temporarily stopping any iron supplements or infusions until your iron levels normalize, as excessive IV iron doses may be associated with an increased risk of cardiovascular events and death, as suggested by recent observational studies 1, 2. The combination of high iron levels and elevated TSH suggests potential issues with both iron metabolism and thyroid function. Your doctor will likely recommend additional tests including a complete iron panel (ferritin, transferrin saturation), thyroid function tests (free T4, free T3), and possibly genetic testing for hemochromatosis. Some key points to consider:
- Elevated hepcidin-25 levels have been linked to fatal and non-fatal cardiovascular events in dialysis patients, and may play a role in the pathogenesis of iron overload-related complications 1.
- Oxidative stress as a result of IV iron infusions and iron overload may represent a ‘second hit’ on the vascular bed, contributing to cardiovascular morbidity and mortality 1.
- Iron deposition in the myocardium of patients with severe iron overload might also play a role in the pathogenesis of sudden death in some patients 1.
- Treatment typically involves addressing both issues separately - managing iron levels through phlebotomy (blood removal) if necessary and potentially starting thyroid medication like levothyroxine (typically starting at 25-50 mcg daily) if true hypothyroidism is confirmed 1, 2. During follow-up appointments, both iron parameters and thyroid function should be monitored regularly until they stabilize within normal ranges. It is essential to note that the toxic effects of excessive iron infusion can be mitigated by careful monitoring and adjustment of iron doses, as well as regular assessment of iron stores and cardiovascular risk factors 1, 2.
From the Research
Implications of Elevated Iron Levels and Hyperthyrotropinemia
- Elevated iron levels and hyperthyrotropinemia (elevated Thyroid-Stimulating Hormone (TSH)) after iron infusion (Intravenous Iron Therapy) may be related to the treatment of iron-deficiency anemia in patients with subclinical hypothyroidism 3.
- Studies have shown that treating subclinical hypothyroidism with levothyroxine plus iron salt is superior to treating with iron salt alone or levothyroxine alone in improving hemoglobin and ferritin levels, as well as reducing TSH levels 4, 3.
- Iron deficiency anemia may lead to alterations in resting metabolic rate (RMR) and thyroid hormone metabolism, and iron supplementation may have varying effects on these parameters 5.
- High-dose intravenous iron repletion may be necessary in certain clinical situations, such as nondialysis-dependent chronic kidney disease, inflammatory bowel disease, and anemia associated with cancer and its treatment 6.
Effects on Thyroid Hormone Levels
- Iron supplementation may affect thyroid hormone levels, with some studies showing an increase in total thyroxine (T4) and others showing a decrease 5.
- The relationship between iron supplementation and thyroid hormone levels is complex and may depend on various factors, including the dose and duration of iron supplementation, as well as the individual's underlying thyroid function 4, 3.
Clinical Considerations
- Clinicians should consider the potential effects of iron infusion on thyroid hormone levels and TSH in patients with subclinical hypothyroidism or iron-deficiency anemia 7, 3.
- Monitoring of thyroid function and iron levels may be necessary in patients receiving intravenous iron therapy, particularly in those with underlying thyroid or hematologic disorders 4, 6.