Normal Thyroid Function Tests Following Discontinuation of Levothyroxine in Hypothyroid Iodine Deficient Individuals

SUMMARY In 28 school children with primary hypothyroidism due to iodine deficiency, 100 µg levothyroxine (L-T4} was administered for nine weeks and resulted in normalization of serum T4, T3, and TSH. Five months after withdrawal of L-T 4 , thyroid function was normal in the majority of subjects. Serum T4 was 8.6±2.3 µg/dl ; T3, 156±2.3 ng/dl; and TSH, 6.9± 12.7 µU/ml. Only one subjects showed subnormal T4. Twenty of 28 subjects still had normal serum TSH ‏below 3.8 µU/ml. Those with increased TSH five months after discontinuation of L-T4 , had lower baseline T4 and T3 and higher TSH, as compared to other subjects. The present finding indicates that the pattern of TSH recovery after withdrawal of thyroid hormone therapy in hypothyroid patients with iodine deficiency differs from reported pattern in subjects residing in iodine sufficient areas.