Search

Congenital hypothyroidism is screened for in the UK using blood spot thyroid-stimulating hormone (TSH) screening at 5-8 d of age. Although standards are set by the UK Newborn Screening Programme Centre, there are variations in TSH cut-offs used. The introduction of repeat screening of preterm babies at 36 weeks' gestational age in 2005 was controversial in its utility and timing. Two cases of preterm babies are presented, who had normal blood spot TSH values on the first test and who became screen positive when re-tested at term. The first with Trisomy 21 was born at 29 + 6 weeks with an initial blood spot TSH of 3.3 mU/L rising to 263 mU/L at term-corrected gestational age (plasma TSH 476.5 mU/L). The second was born at 24 + 6 weeks' gestational age and on day 7, the heel prick blood spot TSH was <2 mU/L, rising to 6.4 mU/L at 36 weeks corrected gestational age. After a barium enema, the plasma TSH increased to 66.6 mU/L with a free thyroxine of 7.6 pmol/L at day 101. Both cases were treated with thyroxine until death due to complications of prematurity. These cases illustrate the difficulties in screening for congenital hypothyroidism in preterm infants, due to the immaturity of the hypothalamo-pituitary-thyroid axis, and the effect of intercurrent illness and drugs on thyroid function. Despite a reassuring published review of 2200 preterm infants, these cases suggest that it may be unwise not to re-screen ex-preterm infants for congenital hypothyroidism at term. [ABSTRACT FROM AUTHOR]

We describe seven infants with transient congenital hypothyroidism (CH) due to maternal thyroid-stimulating hormone receptor (TSH-R) blocking antibodies (TRAb) identified over three decades of newborn screening for CH in Wales, UK that represents a minimum incidence of 1.6% of CH cases. Infants with transient CH due to maternal TRAb presented with a spectrum of clinical and biochemical hypothyroidism. Blood spot TSH concentrations ranged 60.5-332 mIU/L. CH was confirmed by plasma thyroid function tests in all cases (plasma TSH ranged 21-752 mIU/L). The seven infants belonged to five different families. On examination, four infants were clinically hypothyroid. Five infants had a thyroid ultrasound, of which three were abnormal. All infants were treated with thyroxine, which was subsequently withdrawn from three. Following thyroxine withdrawal, one infant resumed normal thyroid function and two developed compensated hypothyroidism. Of the five mothers, two had undiagnosed hypothyroidism and three were receiving thyroxine for longstanding hypothyroidism. Thyroid peroxidase antibody (aTPO) was measured in four and was negative in two, borderline positive in one and strongly positive in another. TRAb was measured in all five women and was strongly positive in all of them. This case series highlights the importance of identifying CH due to TRAb by investigating both the infant and the mother following a raised TSH found on newborn screening. The identification of those infants with transient CH caused by maternal transfer of TRAb is essential for optimizing management during childhood (including potential withdrawal of thyroxine replacement in the longer term) and in any subsequent pregnancy.