Endocrine Abstracts

Objective: To evaluate whether Thyroid peroxidase antibody (anti-TPO) screening is a useful tool in the management of Congenital Hypothyroidism (CH) and determining aetiology.

Background: Thyroid peroxidase (TPO) is essential for thyroid hormone synthesis catalyzing the iodination of tyrosine residues and their coupling to form T3 and T4. It is hypothesized that anti-TPO can cross the placenta, bind to TPO, inhibit its activity in the fetal thyroid gland and result in CH.

Design and Method: We retrospectively evaluated 177 patients, born between May 2019 and May 2021, who had been referred to Great Ormond Street Hospital following an abnormal CH neonatal screening. We retrospectively assessed the infants with a positive anti-TPO status and explored their maternal anti-TPO status, their ongoing management and their 3-year outcome.

Results: Of the 177 infants with an abnormal CH bloodspot TSH screening test, 141 (79.6%) had recorded TPO antibody results. Among these, 11 (7.8%) were positive for anti-TPO, and all required treatment with levothyroxine at diagnosis (TSH 33.5 to >375mU/l). Among the 139 mothers tested, 12 (8.6%) were anti-TPO positive, with 91.7% of their infants also testing positive. Technetium scan showed gland in situ in 4, ectopia in 4, dysgenesis in 3. A follow up US confirmed thyroid tissue was present in 2/3 cases with presumed agenesis. Two children were trialled off levothyroxine before age 3. Both had thyroid scans suggestive of dyshormonogenesis and low normal fT4 at diagnosis (venous TSH 33.5 and 117mU/l). A further five children met the criteria for a trial off treatment at 3 years and one child remained off (venous TSH>375mU/l; fT4,3.9 pmol/l); absent gland on technetium but present on thyroid US.

Conclusion: Anti-TPO was present in 7.8% of our cohort, with a strong correlation to maternal anti-TPO positivity. Anti-TPO were present in infants with confirmed permanent CH and in 3/11 infants were likely to be the aetiological factor with improvement in thyroid function after 5 months and presumed clearance of antibodies. The absence of technetium uptake in a child with anti-TPO and a milder clinical course should prompt US confirmation.