Influence of thyroid function on glomerular filtration rate and other estimates of kidney function in two pediatric patients.

To determine the optimal method of evaluating kidney function in patients with thyroid dysfunction, this study compared the estimated glomerular filtration rate derived from serum creatinine, cystatin C, or ß2-microglobulin with inulin or creatinine clearance in two pediatric patients, one with hypothyroidism and the other with hyperthyroidism. It was observed that the kidney function decreased in a hypothyroid child and enhanced in a hyperthyroid child, with their kidney function becoming normalized by treatment with drugs, which normalized their thyroid function. Kidney function cannot be accurately evaluated using cystatin C-based or ß2-microglobulin-based estimated glomerular filtration rate in patients with thyroid dysfunction, as these tests overestimated glomerular filtration rate in a patient with hypothyroidism and underestimated glomerular filtration rate in a patient with hyperthyroidism, perhaps through a metabolic rate-mediated mechanism. In both our patients, 24-h urinary creatinine secretion was identical before and after treatment, suggesting that creatinine production is not altered in patients with thyroid dysfunction. Therefore, kidney function in patients with thyroid dysfunction should be evaluated using creatinine-based estimated glomerular filtration rate.

Assessment of kidney function in children by enzymatic determination of 2- or 24-h creatinine clearance: comparison with inulin clearance.

BACKGROUND: Although renal inulin clearance (Cin) is the gold standard for evaluation of kidney function, it cannot be measured easily. Therefore, creatinine clearance (Ccr) is often used clinically to evaluate kidney function. Enzymatically measured Ccr was recently found to be much higher than Cin because of the tubular secretion of creatinine (Cr). This study compared three measures of renal clearance, inulin, 2-h Ccr, and 24-h Ccr, in children. METHODS: Kidney function was evaluated in 76 children (51 males and 25 females) aged 1 month to 18 years with chronic kidney disease (CKD) by three renal clearance methods at almost the same time. RESULTS: Correlations between each pair of three renal clearance measurements were determined. Approximate glomerular filtration rate (GFR) was equal to 62 % of 2-h Ccr or 76 % of 24-h Ccr. CONCLUSION: Cr secretion by renal tubules was approximately 50 % of the GFR. In this study, we indicate that the measurements of 2-h Ccr or 24-h Ccr do not show true GFR but we could infer approximate GFR from the values. The use of 2- or 24-h Ccr might contribute to the treatment of pediatric CKD patients.

Three year outcome of childhood idiopathic nephrotic syndrome under a unified immunosuppressive protocol.

BACKGROUND: This retrospective study was performed to assess the 3 year outcome of a unified protocol for childhood idiopathic nephrotic syndrome. METHODS: Cyclosporine A (CsA) or CsA plus mycophenolate mofetil (MMF) were used in patients without remission on high-dose steroid therapy. CsA was maintained at an area under the whole blood concentration-time curve up to 4 h after dose (AUC0-4 ) of 1500 and 2000 ng·h/mL in steroid-dependent nephrotic syndrome (SDNS) and steroid-resistant nephrotic syndrome (SRNS), respectively. Ninety-one children were enrolled in the study (SDNS, n = 64; SRNS, n = 18). Patients were divided into minimal change (MC) and focal segmental glomerulosclerosis (FSGS) groups. Three year outcome was evaluated using clinical severity defined as degree of dependence on immunosuppressive therapy for maintenance of remission. RESULTS: In the SDNS group, the numbers of MC and no biopsy were 51 and 13, respectively. No patient had FSGS. Twelve SRNS patients had FSGS and six had MC. In SDNS, 15/64 patients (23%) received no medication. CsA was effective as steroid-sparing agent in 31/38 patients (82%). MMF was effective in all eight patients for whom CsA was unsuccessful. Remission rate in the SRNS group was 14/18 (78%; eight with CsA, and six with a combination of CsA + MMF). Five of the 14 SRNS remission patients received methylprednisolone pulse therapy. Four were resistant to therapy, and had impaired renal function. The clinical severity of MC and FSGS overlapped. CONCLUSIONS: Treatment with CsA and combination of CsA plus MMF was useful for SDNS and for remission induction in SRNS.

Effect of hemolytic and iron-deficiency anemia on intestinal absorption and tissue accumulation of cadmium.

Abnormal iron (Fe) metabolism induces iron-deficiency anemia (FeDA) and also affects body cadmium (Cd) accumulation. However, whether hemolytic anemia also affects Cd metabolism is not known. We compared the intestinal absorption and tissue accumulation of Cd after oral administration of Cd to mice with hemolytic anemia induced by treatment with phenylhydrazine (PHA mice) to that in mice with FeDA. Although the hematocrit decreased significantly in mice with either type of anemia, the Fe concentration decreased in the livers and kidneys of FeDA mice, but increased in those of PHA mice. After an oral administration with various amounts of Cd, hepatic and renal Cd concentrations significantly increased in both FeDA and PHA mice. An intraduodenal injection of Fe raised the hepatic Fe content in FeDA mice to the control level and raised the hepatic Fe content in PHA mice to 2.4 times that in control mice. Intestinal divalent metal transporter 1 (DMT1) expression increased significantly in mice with both types of anemia. These data indicate that, despite the accumulation of hepatic Fe associated with PHA, PHA also significantly increases hepatic and renal Cd accumulation according to an stimulation of intestinal DMT1 expression, as occurs in FeDA mice. This suggests that anemia may be a risk factor for Cd accumulation.