Endocrine Abstracts

Introduction: Neonatal biochemical screening programmes for congenital hypothyroidism (CH) allow early diagnosis and treatment of infants with CH, thereby efficiently preventing mental retardation. The purpose of the study was to assess the predictive role of Tc-99m pertechnetate thyroid scintigraphy in differentiating between transient and permanent hypothyroidism in neonates with borderline TSH results (6–19.9 μ/l) at the screening.

Methods: A retrospective review of 29 neonates (19 males and 10 females) with borderline TSH results at newborn screening between January 2006 and December 2007 was performed. The thyroid scan was acquired 20–30 min after i.v. injection of 1–5 MBq/kg of Tc-99m pertechnetate. Thyroid tracer uptake was graded visually as low (less than equal tosalivary gland uptake), normal (greater than salivary and background uptake) and high (no significant salivary or background uptake seen). The patients were classified in two groups based on thyroxine requirements at 3 years of age. One group included seven children with no requirement of thyroxine replacement (transient hypothyroidism). The other group included 22 children on lifelong thyroxine replacement (permanent hypothyroidism). The pattern of thyroid uptake was evaluated in each group.

Results

Within the group with transient hypothyroidism (seven patients) there was low, normal or high thyroid tracer uptake in 1 (14%), 2 (29%) and 4 (57%) children respectively. The mother of the child with low uptake had raised TSH antibodies. Within the group with permanent hypothyroidism (22 patients), there was low, normal or high thyroid uptake in 3 (14%), 12 (55%) and 7 (31%) children respectively. Only one child had an ectopically located thyroid tissue, the other children had a normally located thyroid.

Conclusion: In this small group of neonates with borderline high TSH on screening the majority of babies with low or normal tracer uptake on thyroid scan had permanent hypothyroidism. Babies with high uptake had either transient or permanent hypothyroidism.