Thyroid hormone replacement therapy for primary hypothyroidism leads to significant improvement of renal function in chronic kidney disease patients

The interactions between kidney and thyroid functions have been known for many years; however, there are few studies on the extent of the improvements and long-term changes of renal function after thyroid hormone replacement therapy (THRT) in chronic kidney disease (CKD) patients. The purpose of this study was to determine how THRT affects the estimated glomerular filtration rate (eGFR) in CKD patients with primary hypothyroidism. A retrospective investigation was performed on 51 Japanese patients (15 men and 36 women) with primary hypothyroidism. The changes in eGFR after THRT were examined according to the existence of CKD and severity of thyroid function. eGFR increased rapidly over the first 6 months after THRT in CKD patents, which was followed by a plateau. There was a correlation between eGFR and the severity of hypothyroidism, which was independent of age, and eGFR in severely hypothyroid patients significantly increased up to levels that were similar to mildly hypothyroid patients after THRT. eGFR improved more in the lower initial eGFR group and increased about 30 % in CKD patients (47.5 +/- A 7.7 vs. 62.1 +/- A 9.5 ml/min/1.73 m(2), P < 0.01). Moreover, eGFR in CKD patients with mild to moderate hypothyroidism was significantly increased compared to that in non-CKD patients. Our data suggested that hypothyroidism contributed to the reduction in eGFR, especially in CKD patients; therefore, patients with CKD should positively be examined for thyroid function, and appropriate THRT should be started if needed.