530 - Timeline of Conversion of Autoimmune Subclinical Hypothyroidism to Overt Hypothyroidism in Children

Poster Number: 530
Publication Number: 530.107

Hope Clennon, Maimonides Infants and Children's Hospital of Brooklyn, North Brunswick, NJ, United States; Yelena Kogelman, Maimonides Infants and Children's Hospital of Brooklyn, Brooklyn, NY, United States

Background: Hypothyroidism is the most common disturbance of thyroid function in children and can be congenital or acquired. Acquired hypothyroidism is most often caused by autoimmune thyroiditis and may be either subclinical (elevated serum thyroid-stimulating hormone [TSH] (6-10 mU/L) with normal serum free thyroxine [T4] concentrations) or overt (elevated TSH and normal or low free T4 concentrations). Of the wide range of children (10-40%) (1,2,5) who may progress from subclinical autoimmune hypothyroidism progress to overt clinical hypothyroidism, there is no definitive time period that it typically takes for conversion to occur. (4) As a result, patients with subclinical hypothyroidism require frequent monitoring of thyroid function tests. (3) Identifying this time period may contribute to decreasing the frequency of monitoring by showing the natural progression of autoimmune hypothyroidism in this sample group of children.

Objective: Our objective was to determine the typical length of time of conversion from subclinical to clinical hypothyroidism. We hypothesized that a child with subclinical autoimmune hypothyroidism can be expected to convert to clinical autoimmune hypothyroidism within a predictable time period, most likely 6 months to 1 year (180 – 365 days). Otherwise, the child can be expected to revert to euthyroidism.

Design/Methods: This is a retrospective cohort study of pediatric children ages 3- 18 years old, documented to have acquired autoimmune hypothyroidism who were seen in the endocrinology clinic at Maimonides Medical Center located in Brooklyn, NY from January 2010 to December 2020. Our EMR was queried to identify children meeting ICD 10 diagnosis codes consistent with acquired hypothyroidism (E03.9) and Hashimoto thyroiditis (E03.8) who had lab orders for TSH, FT4, TPO antibodies, and thyroglobulin antibodies. Their index abnormal TSH values were identified (5.00 – 9.99 mIU/L), and we tracked the time to normal (TSH 0.40 – 5.00 mIU/L) or elevated values (TSH > 10.00mIU/L).

Results: A total of 95 children met the criteria for analysis with an initial subclinical TSH level. The median time to the change from subclinical range to euthyroidism or clinical hypothyroidism was 132 days.Conclusion(s): This study demonstrated that most children with autoimmune subclinical hypothyroidism will have a definitive change in their TSH values to clinically euthyroid or hypothyroid levels in a time period of approximately 4 months. While the sample size is small, results may contribute existing literature and potentially decrease prolonged or invasive testing in these patients.