SAN DIEGO – Chronic kidney disease patients with subclinical hypothyroidism who were treated with thyroid hormone had better preserved renal function than did those who did not receive the treatment, a study has shown.
In addition, thyroid hormone replacement therapy was an independent predictor of renal outcomes in this subset of patients, Dr. Shin-Wook Kang reported at Kidney Week 2012.
"Subclinical hyperthyroidism is not a rare disorder, especially in females and in the elderly, and it is frequently observed in CKD [chronic kidney disease] patients," said Dr. Kang of the department of internal medicine at Yonsei University College of Medicine, Seoul, Korea. "In contrast to overt hypothyroidism, thyroid hormone treatment is seldom necessary in patients with subclinical hypothyroidism. Even though previous studies have demonstrated that thyroid hormone improves cardiac dysfunction and reduces total and LDL cholesterol levels in patients with subclinical hypothyroidism, the impact of thyroid hormone replacement therapy on renal function has never been studied in these patients."
Dr. Shin-Wook Kang
In an effort to investigate whether restoration of euthyroidism is beneficial in terms of preserving renal function in CKD patients with subclinical hypothyroidism, he and his associates retrospectively studied the medical records of 309 patients with stage 2-4 CKD who were diagnosed with subclinical hypothyroidism and treated at the college of medicine during 2005-2010. They assessed demographic, clinical, and biochemical data including levels of calcium/phosphorus, albumin, total cholesterol, and triglycerides and estimated glomerular filtration rate (GFR). The researchers used a linear mixed model to compare changes in estimated GFR over time between patients who received thyroid hormone replacement therapy and those who did not.
Of the 309 patients, 180 (58%) were treated with l-thyroxine at an initial dose of 25 mcg/day (treatment group) while the remaining 42% were not (nontreatment group). Among patients in the treatment group, the dose of l-thyroxine was adjusted 5-6 weeks after the start of therapy and then every 3 months based on the patient’s serum TSH levels.
At baseline, levels of serum cholesterol and triglyceride were significantly higher in the treatment vs. the nontreatment group (180.0 vs. 161.3 mg/dL and 162.7 vs. 125.6 mg/dL, respectively).
During a mean follow-up of 34.8 months, the overall rate of decline in estimated GFR was significantly greater in the nontreatment group than in the treatment group (–5.93 vs. –2.11 mL/min per year per 1.73 mm2). Dr. Kang also reported that a linear mixed model showed a significant difference in the rates of estimated GFR over time between the two groups, while Kaplan-Meier analysis also showed that renal event-free survival was significantly higher in the treatment group.
Multivariate Cox regression analysis revealed that thyroid hormone replacement therapy was an independent predictor of renal outcome (hazard ratio, 0.28; P =.01).
"Thyroid hormone therapy not only preserved renal function better but also was an independent predictor of renal outcome in CKD patients with subclinical hypothyroidism, suggesting that thyroid hormone replacement should be considered in these patients," Dr. Kang said.
Dr. Kang said he had no relevant financial conflicts to disclose.