TRANSIENT NEONATAL HYPOTHYROIDISM IN A PATIENT WITH A DE NOVO MUTATION IN THE THYROID HORMONE RECEPTOR BETA GENE

STIVEL, MIRTA; RIVOLTA, CARINA MARCELA; ONETO, A.; MACCAILINI, G.; ARANDA, C.; TARGOVNIK, HÉCTOR MANUEL

Mar del Plata, Argentina

Congreso; XIX Reunión Anual de la Sociedad Latinoamericana de Endocrinología Pediátrica (SLEP); 2007

Sociedad Latinoamericana de Endocrinología Pediátrica (SLEP)

Resistance to Thyroid Hormone (RTH) is an inherited disorder of reduced responsiveness of the target tissues to thyroid hormone (TH) usually suspected when elevated TH are associated with non suppressed TSH. Basal TSH levels are normal or slightly increased and because screening programs are based on the determination of TSH, only few data of RTH are available during the neonatal periodo. We present a child with transient neonatal hypothyroidism most likely related to iodine overload subsequently diagnosed as having RTH. A 12-day-old boy delivered by cesarean section at term was referred due to borderline TSH at screening (9.2mIU/I). He was breast fed and the mother was disinfected daily with povidone iodine. TSH was elevated (101 mlU/l), FT4 was normal (1.3l ng/dl) and Tg was markedly elevated (1.200 ng/ml) at 12 days of age. Thyroid US and 99Tc scan revealed an enlargement ofthe gland. Treatment with T4 was initiated but discontinued after 3 months, owing to significantly elevated FT4. After 1 month without treatment, FT4 was elevated (4.2 ng/dl) with non suppressed TSH (6.6 mlU/l). TRH/TSH test was higher respondent (33.7 mIU/I). RTH was confirmed by detection of a heterozygous mutation (P453T) in the T3 receptor-beta gene. The mutation was absent in the parents. We conclude that in this infant the increased iodine load during the neonatal period impaired the ability of the thyroid gland to supply adequate amounts of TH allowing the initiation of a prompt T4 treatment of the hypothyroid state and the early detection of RTH due to a de novo mutation in the T3beta receptor gene.