Effect of Transient Neonatal Hyperthyrotropinemia on Intellectual Quotient and Psychomotor Performance

Background: Transient neonatal hyperthyrotropinemia (TNH) occurs frequently in areas of iodine deficiency and may affect intellectual function and psychomotor performance. Design: A historical cohort study of intellectual development, psychomotor performance, urine iodine and thyroid function tests, performed in 9 years children with documented TNH at birth and control group. Subjects: Eighteen (18) children who had been born in Mahdieh hospital were studied at age 9 with TNH in 1987-88 and compared to 19 matched children born in the same time, but having normal thyroid function at birth. Measurment: Global intelligent (IQ) and psychomotor performance were evaluated with Raven and Bender-Gestalt tests, respectively. Total T4, and T3 were measured by commerical RIA ana TSH were measured by IRMA. Urine was tested for iodine content by digestion method. Results: Height and weight were similar in two groups at birth and at 9 years of age. Thyroid function test were similar in two groups except for TSH at birth, which was higher in TNH than in control group (23.4±8.3 vs 3.6±1.0 µU/ml, P<0.001). Results of T4, T3, and T3,Rupt and urinary iodine concentration at 9 years of age were not different between two groups. Mean IQ was 98±11 and 106±8 in TNH and normal children, respectively (P<0.01). There was no significant difference between psychomotor performance in two groups. There was no correlation between TSH at birth and IQ at 9 years of age. Canclusion: Infants born in an area lodine deficiency, who had TNH at birth, had lower IQ at the age of 9 years than matched controls living in the same environmental conditions but with normal thyroid function at birth. The present finding suggests that TNH may adversely affect longterm intellectual development.