From the Research
High levels of free thyroxine (FT4) can potentially worsen kidney function, as evidenced by a prospective investigation that found higher FT4 levels were associated with an increased risk of incident chronic kidney disease (CKD) and rapid decline in renal function 1.
Key Findings
- Elevated thyroid hormones, as seen in hyperthyroidism, increase the metabolic rate throughout the body, which affects kidney function by increasing renal blood flow and glomerular filtration rate.
- Hyperthyroidism may also cause proteinuria (protein in urine) and can exacerbate existing kidney disease.
- The cardiovascular effects of hyperthyroidism, such as increased heart rate and blood pressure, can indirectly impact kidney health by altering renal perfusion.
Recommendations
- Patients with elevated FT4 levels should have their kidney function monitored regularly through blood tests measuring creatinine and estimated glomerular filtration rate (eGFR).
- Treatment of the underlying thyroid condition with medications like methimazole or propylthiouracil, or in some cases radioactive iodine therapy or surgery, is essential to prevent kidney complications, as supported by studies comparing the efficacy of these treatments 2, 3.
- Maintaining proper hydration is also important as hyperthyroidism increases the risk of dehydration, which can further stress the kidneys.
Considerations
- The relationship between thyroid hormones and kidney function is complex, and both high and low levels of thyroid hormones can have adverse effects on the kidneys, as suggested by a study analyzing the association between TSH and kidney function 4.
- The choice of treatment for hyperthyroidism should be individualized based on the underlying diagnosis, the presence of contraindications, and the patient's preference, as outlined in a review of hyperthyroidism diagnosis and treatment 5.