Background & Aims: Iodine is an essential element of biosynthesis of thyroid hormones and for the development of the fetus nervous system during early pregnancy. It has been suggested that alteration in iodine clearance during pregnancy is dependent on glomerular filtration rate (GFR). The aim of the present investigation was to explore the association between urinary iodine excretion (UIC) and serum cystatin C during pregnancy.

Materials & Methods: In this cross-sectional study, 74 pregnant women (age>17 years) at first trimester (< 12 weeks) were enrolled. Random urine and serum were collected at first-, second- and third trimesters. UIC was assayed according to Sandell-Kolthoff reaction, cystatin C by PETIA technique and serum creatinine by the Jaffe method, respectively. Data analysis was performed using SPSS software (version 22.0).

Results: The mean age of the studied population was 26±5 years. Median UIC at first-, second- and third trimesters were 57 µg/L, 126 µg/L and 89 µg/L (P<0.0001). Mean cystatin C levels were 0.71±0.2 mg/L, 0.74±0.2 mg/L and 0.98±0.3 mg/L (P=0.001). Serum creatinine concentrations were 0.83±0.1 mg/dL, 0.81±0.1 mg/dL and 0.82±0.1 mg/dL. No significant relationships between was seen between UIC and cystatin C during gestation.

Conclusions: This study reveals that serum cystatin C levels during first and second trimesters were similar but significantly higher that of the third trimester. The pattern of UIC alteration during pregnancy did not match that of cystatin C. These findings imply that the marked reductions in UIC during first and third trimesters relative to that of the second trimester does not reflect increased GFR but is to ensure adequate iodine supply for thyroid hormone biosynthesis during the two vital stages of pregnancy.

SOURCE: URMIA MED J 2016: 27(1): 90 ISSN: 1027-3727