The glomerular filtration rate (GFR) decreases with age, while parathyroid hormone (PTH) increases. There are a few reports only on the relationship between GFR and PTH under the category of serum 25-hydroxyvitamin D (25[OH]D) concentration.

Using the Korea National Health and Nutrition Examination Survey (KNHANES) data, a cross-sectional study was conducted on the association between serum 25(OH)D concentration, GFR and PTH in Korean adults aged 50 years or older. Serum PTH concentration was compared to the tertiles of GFR after adjustment for relevant variables. In addition, the serum PTH concentration was compared with the GFR under the category of serum 25(OH) D concentration (<20, 20-30, >30 ng/mL).

The mean estimated GFR (eGFR) was 74.8 mL/min in men and 73.1 mL/min in women. The mean PTH and 25(OH) D was 66.8 pg/mL, 20.5 ng/mL in men and 69.0 pg/mL, 18.2 ng/mL in women. The serum PTH concentration showed a significant negative correlation with the serum 25(OH) D and eGFR in both genders. The serum PTH concentration significantly increased at the lower tertile of eGFR in male adults In addition, a decrease of serum PTH concentration was marked in the vitamin D sufficient male adults (>30 ng/mL).

This present study demonstrated that serum PTH concentration showed negative correlation with eGFR, however, serum PTH increase may be minimized by maintaining proper serum 25(OH)D concentrations under similar eGFR status in Korean adults aged 50 and above.

Abnormal serum gamma-glutamyltransferase (γ-GT) may be an early and sensitive marker for oxidative stress. This study was performed to evaluate the association between serum heavy metals and γ-GT concentration.

This study is a cross-sectional analysis based on data from Korean National Health and Nutrition Examination Survey (V-1, 2, 2010, 2011) regarding serum heavy metal concentrations (lead, mercury, and cadmium) as well as serum γ-GT. Serum heavy metals were categorized into tertiles, and serum γ-GT concentration was compared using an analysis of covariance test after relevant variable adjustments. In addition, we evaluated the odds ratio (OR) of having the highest tertile of serum γ-GT in each heavy metal tertile using logistic regression.

The mean serum lead, mercury, and cadmium concentrations were 2.67, 5.08, and 1.02 µg/dL in men and 1.95, 3.60, and 1.21 µg/dL in women, respectively. Partial correlation showed a significant positive relation between each heavy metal and serum γ-GT concentration. Comparing serum γ-GT concentration by the tertile of each heavy metal, serum γ-GT concentration showed a significant increase as the tertiles of serum mercury and cadmium in men and that of serum mercury in women increased, but not with lead. The OR of having the highest tertile of serum γ-GT was significant for cadmium in men (OR, 4.02; 95% confidence interval [CI], 2.54 to 6.35) and mercury in women (OR, 2.00; 95% CI, 1.29 to 3.10) in the top tertile of each heavy metal.

Higher serum heavy metal concentration may be related with higher serum γ-GT concentration. In particular, serum cadmium in men and mercury in women showed significant correlation with serum γ-GT concentration.