EVALUATION OF THE RELATIONSHIP BETWEEN URINARY IODINE EXCRETION AND SERUM CYSTATIN C DURING GESTATION

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.