Thyroid stimulating hormone levels in cord blood are not influenced by non-thyroidal mothers' diseases.

CONTEXT: Screening programs not only offer the opportunity to trace and treat almost all cases of congenital hypothyroidism but also mean large savings to the health system. However, carefully planned strategies are necessary to extend their benefits and reduce costs.

OBJECTIVE

To determine the possible influence of maternal diseases that affect maternal-fetal placenta dynamics on primary thyroid stimulating hormone (TSH) screening for congenital hypothyroidism.

DESIGN

Prospective non-randomized clinical trial with at least 3 months of follow-up.

SETTING

A public university referral center [CAISM/Hospital das Clínicas, Faculty of Medicine, University of Campinas, Campinas, SP].

PARTICIPANTS

415 neonates divided into 5 groups: eighty-three infants born from cardiac mothers; 98 from mothers that had toxemia; 54 of the mothers had diabetes mellitus; 40 were HIV positive and 140 had no diseases.

INTERVENTION: All newborns had cord blood samples collected on filter paper at birth.

MAIN MEASUREMENTS: TSH was measured from dried blood spots using a homemade immunofluorescence assay (sensitivity in dried blood spots = 0.1 mU/L).

RESULTS

There was no significant difference in the mean TSH levels among the 5 groups. Moreover, TSH levels were around 5 mU/L in 48% of the newborns, indicating that our region is severely deficient in iodine.

CONCLUSIONS

Our results indicate that primary TSH screening programs using cord blood are not affected by maternal diseases. We suggest that, besides its technical advantages over heel punctures with T4 primary approaches, neonatal screening using primary cord blood TSH may also be used as a monitoring tool for evaluation and control of iodine deficiency disorders (IDD).