Congenital hypothyroidism with delayed TSH elevation in low-birth-weight infants: incidence, diagnosis and management

In our neonatal program, a number of infants with congenital hypothyroidism (CH) had escaped diagnosis, when a spot RIA-TSH value of 20 mU/liter whole blood was used as a cutoff point. The objective of the study was to find out prospectively the additional number of newborns with CH if the TSH cutoff point is lowered to 10 mU/liter. The study included 311,390 screened newborns. The children with CH were followed up for a period of 3 yr. Twenty-eight percent of infants diagnosed with CH had neonatal TSH values between 10 and 20 mU/liter (56 of 200). Forty of 47 infants, who were reevaluated later on (85.1%), suffered permanent CH. A thyroid scintiscan and/or echogram revealed that eight of 40 children (20.0%) had a structural defect, and the remaining (32 of 40) had a functional defect of the thyroid gland without anatomical abnormality; 14 of 32 cases were familial. Eighteen of the 47 reevaluated infants were prematurely born (38.3%) and 15 of these 18 had permanent CH (83.3%). The lowering of TSH cutoff point from 20 to 10 mU/liter resulted in a 10-fold increase of recall rate. A significant number of cases with permanent CH are missed when a TSH threshold of 20 mU/liter is applied. Almost 40% of the missed CH cases were premature. A mild increase of TSH at screening is not a predictor of transient CH. The increase in recall rate constitutes a serious drawback and should be balanced against the possible consequences of thyroid dysfunction at this important developmental stage.

To test the hypothesis that very low birth weight (VLBW) and extremely low birth weight (ELBW) infants have an increased incidence of congenital hypothyroidism (CH) with a delayed thyroid-stimulating hormone (TSH) elevation and that the outcomes of these infants are similar to control infants. Retrospective analysis of newborn thyroid screening data for 92 800 live births in Rhode Island to identify CH with a delayed TSH elevation. Developmental, growth, and endocrine outcomes of the index cases were assessed at 18 months corrected age. CH with a delayed TSH elevation occurred in 1 in 58 ELBW, 1 in 95 VLBW, and 1 in 30 329 infants weighing ≥1500 grams (P < .0001). The incidence of head circumference <10(th) percentile was higher in VLBW infants with CH associated with a delayed TSH elevation (P < .05), and the mean head circumferences, weights, lengths, and developmental scores were similar to matched control infants. Three infants received short-term levothyroxine replacement. The incidence of CH with a delayed TSH elevation was higher in ELBW and VLBW infants compared with infants weighing ≥1500 grams. The outcomes of these infants were comparable with matched control infants. Copyright © 2011 Mosby, Inc. All rights reserved.

To determine the evolution of congenital hypothyroidism in preterms and the clinical features of permanent forms.