TOPICAL IODINE AND NEONATAL-HYPOTHYROIDISM

Objectives: To determine whether skin care practices with iodine-conta ining disinfectants are putting patients in the neonatal intensive car e unit al risk for primary hypothyroidism. Cutaneous exposure to povid one-iodine antiseptic solutions may be a cause of primary hypothyroidi sm in neonates. Design: Prospective pilot study. Setting: Level III ne onatal intensive care unit of a university-affiliated hospital. Partic ipants: Sequential sample of 47 medical and surgical patients admitted to the neonatal intensive care unit who received cutaneous povidone-i odine applications in preparation for invasive or surgical procedures. Methods: Seven to 10 days after iodine exposure, capillary blood samp les were obtained on filter paper blots for thyroid function testing a nd urine samples were collected to determine quantitative iodine conce ntrations. A plasma creatinine level was determined for each subject. Results: A total of 47 patients were enrolled. The gestational ages of subjects ranged from 26 to 41 weeks (mean, 33.6 weeks); the male-to-f emale ratio was 28:19; and the birth weights ranged from 0.7 to 5.1 kg (mean, 2.42 kg). The thyroxine level ranged from 20 to 187 nmol/L (1. 6 to 14.6 mu g/dL) (mean, 102 nmol/L [7.9 mu g/dL]; reference, greater than or equal to 90 nmol/L [greater than or equal to 7 mu g/dL]); and the thyrotropin level ranged from 0.1 to 16.5 mU/L (mean, 6.4 mU/L; r eference, <20 mU/L). The mean urine iodine concentration was 2798.0 mu g/dL (reference, <40 mu g/dL), and the mean plasma creatinine level w as 60 mu mol/L (0.69 mg/dL) (reference, less than or equal to 50 mu mo l/L [less than or equal to 0.6 mg/dL] for males and less than or equal to 40 mu mol/L [less than or equal to 0.5 mg/dL] for females). Conclu sions: There was no documentation of primary hypothyroidism in our sub jects despite elevated urine iodine levels. While it is still possible that patients who receive long-term iodine exposure in other settings leg, cardiac catheterization) are at risk for primary hypothyroidism, our study suggests that the amount of iodine absorbed through routine neonatal intensive care unit procedures does not substantially alter thyroid function during the first 10 days of life, An important confou nding variable is that seven patients were receiving dopamine hydrochl oride infusions and four were receiving dexamethasone phosphate at the time of sample collection. We therefore cannot rule out the possibili ty that these medications masked a thyrotropin level elevation that wo uld have occurred in a primary hypothyroid state. We discuss implicati ons for the interpretation of the results of neonatal thyroid function tests.