Effect of Transient Neonatal Hyperthyrotropinemia on Intellectual Quotient and Psychomotor Performance

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.

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.