Newborn Screening for Thyroid-stimulating Hormone as an Indicator for Assessment of Iodine Status in the Republic of Macedonia

Abstract

SummaryBackgroundIodine deficiency is associated with goiter and impaired brain function leading to cretinism. An increased frequency of thyroid-stimulating hormone (TSH) measurements above 5 mlU/L on newborn screening points toward an impaired iodine status of the population.MethodsA 13-year retrospective analysis was performed in 228,266 newborns participating in the national thyroid newborn screening program. The TSH concentration was measured in dry blood spots collected by heel stick on filter paper, 48 hours after birth, using fluoroimmunometric DELFIA method.ResultsOut of 236,378 live-born infants, 228,266 (96.6%) have been screened for TSH, of which 198,213 (86.8%) were retrospectively evaluated for TSH levels above 5 mlU/L. Neonates with congenital hypothyroidism, prematurity, and low birth weight were excluded from the evaluation, as well as the inadequately sampled neonates (13.2%). A national prevalence of 3.08% newborns (n=6,105) with TSH > 5 mIU/L was found. Higher percentages were noted in two regions of the country, indicating possible mild iodine deficiency in these regions and shifting the overall average to above 3%.ConclusionsOur results indicate overall iodine sufficiency in the Macedonian population. Additional assessment of the iodine intake in the regions with suspected mild iodine deficiency is needed to prevent suboptimal cognitive and psychomotor outcomes.

Direct Estimation of Reference Intervals for Thyroid Parameters in the Republic of Srpska

“…Although these studies used ultrasound to rule out non-obvious or potential abnormalities of the thyroid gland, this should not be the reason for non-compliance with our results, because there are no recommendations for necessary ultrasound examination of the thyroid gland by the NACB ( 6 ). Our results are not similar to the results of studies in which ultrasound was not used for the assessment of patients’ health status ( 21 , 22 ). The reference values of thyroid hormones are dependent on the population, methodology and apparatus on which the analysis is performed, as our study confirmed ( 23 – 26 ).…”

Regional Variation in the Incidence of Congenital Hypothyroidism in Macedonia

“…This is in accordance with our finding that 4.44% of the screened newborns in the Vardar region had a TSH concentration above 5 mIU/L whole blood, as an indicator of iodine deficiency, in comparison with the Eastern region where only 1.66% of newborns had TSH>5 mIU/L. Possible mild iodine deficiency in the Vardar region has been described previously [23]. Iodine intake at the population level is a major determinant of thyroid function, and decreasing intake is reflected in increasing neonatal TSH levels [24,25].…”

“…This may be due to iodine deficiency, although Macedonia as a whole is no longer recognized as an iodine-deficient area [22]. However, some regions might still belong to iodine-deficient areas [23]. This is in accordance with our finding that 4.44% of the screened newborns in the Vardar region had a TSH concentration above 5 mIU/L whole blood, as an indicator of iodine deficiency, in comparison with the Eastern region where only 1.66% of newborns had TSH>5 mIU/L.…”

Diagnostic re-evaluation of congenital hypothyroidism in Macedonia: predictors for transient or permanent hypothyroidism

“…( 3 ). A recently published study accessing the iodine status through TSH measurements on newborn screening reported iodine sufficiency in Macedonia ( 21 ). Considering these facts the etiology of the most of our TCH cases remains unknown.…”