176: Lithium intake during pregnancy leading to large goiter and subclinical hypothyroidism in a prematurely born baby

Abstract

A premature baby with a large goiter was born from a mother treated during the whole gestation with lithium (750 mg/d). Tracheal compression was visible on a lateral neck x-ray. Skeletal maturation was retarded and a hyperbilirubinemia prolonged. On the second day plasma TSH was elevated to 118 uU/ml and total thyroxin was 12,5 ug %. 100 ug of TRH i.v. increased plasma TSH at 30 and 60' above 200 uU/ml. After two weeks treatment with L-thyroxin basal TSH was still elevated. After a further two weeks plasma TSH response to TRH was suppressed and the size of the goiter reduced. Somatic and psychomotor development was slightly retarded. In order to decide on the necessity of continuation of therapy a TRH-test was repeated at the age of 6 months. Substitution was therefore interrupted for 2 weeks and resumed immediately after TRH stimulation until laboratory results were available. As T4, T3 and the pattern of TSH were euthyroid therapy was definitively withdrawn A TRH-test in the mother revealed a borderline hypothyroidism: basal T4 at lower limit of normal TSH rise exaggerated. It is concluded that lithium intake during pregnancy can induce hypothyroidism. TRH-stimulation is a sensitive parameter for borderline hypothyroidism. The test is useful for the decision for withdrawal of replacement therapy started as a preventive measure in suspected cases of hypothyroidism in newborns.