Correlation between urinary iodine levels and TSH of umbilical cord from newborns of the University Hospital at the School of Medicine from Ribeirão Preto, São Paulo

The safest and most efficient way to diagnose congenital hypothyroidism (CH) is through screening programs using serum thyroid stimulating hormone (TSH). CH occurs in one in 1:2,300-1:5,000 births but higher rates are found in iodine-deficient areas. Iodine was measured in the urine of 141 newborns (87 males and 54 females) from Ribeirão Preto to complement the screening program developed by the School of Medicine of Ribeirão Preto (FMRP-USP) and Federal University of São Paulo (UNIFESP). TSH values did not disclose any case of CH, although we have seen an elevated ratio (0.96%) of calls for retests. The iodine urinary levels ranged from 2.1 to 194 microg/l (mean 58.3+/-36.2 microg/l). No differences between the levels of urinary iodine and gender or gestational ages were observed. A negative correlation between urinary iodine and TSH of blood from umbilical cord was found (r= -0.20, p= 0.02).