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Identification and characterization of two groups of congenital hypothyroid infants: implications for newborn
I E Auger1, R Bellisario, S Koerner-Rabatoy
1Wadsworth Center for Laboratories and Research, New York State Department of Health, Albany 12201-0509, USA.
Insights
This study analyzed 400 newborns with congenital primary hypothyroidism. A TSH cutoff of 50 mU/l effectively distinguished two infant groups, aiding in diagnosis and understanding disease characteristics.
Area of Science:
- Pediatrics
- Endocrinology
- Neonatal screening
Background:
- Congenital primary hypothyroidism requires early diagnosis for proper management.
- Newborn screening programs utilize thyroid-stimulating hormone (TSH) and thyroxine (T4) levels.
- Distinguishing true cases from false positives is crucial for timely intervention.
Purpose of the Study:
- To analyze congenital primary hypothyroidism cases based on newborn screening TSH values.
- To identify distinct infant groups using a TSH cutoff of 50 mU/l.
- To evaluate the predictability of screening parameters for follow-up TSH levels.
Main Methods:
- Retrospective analysis of 400 newborns diagnosed with congenital primary hypothyroidism (1983-1987).
- Case group separation based on newborn screening TSH values using a normal probability plot (TSH cutoff at 50 mU/l).
- Statistical evaluation of TSH, T4, birthweight, sex, and age at sampling for predictive value.
Main Results:
- Two distinct groups of infants were identified with TSH < 50 mU/l and TSH > 50 mU/l.
- Infants with TSH < 50 mU/l showed a higher proportion of males and low birthweight, with T4 increasing with TSH.
- Screening TSH, T4, and birthweight predicted follow-up TSH in the TSH > 50 mU/l group, but not in the TSH < 50 mU/l group.
Conclusions:
- A TSH cutoff of 50 mU/l effectively categorizes newborns with congenital primary hypothyroidism.
- Screening parameters have differential predictive value for follow-up TSH based on the initial TSH level.
- An optimal screening rule based on T4, TSH, and their interaction is proposed.
Abstract:
A retrospective analysis of 400 newborns diagnosed with congenital primary hypothyroidism between 1983 and 1987 was conducted. Two distinct groups of cases were identified and characterized based on their newborn screening TSH value. The two groups are separated at a TSH concentration of 50 mU/l of serum by a normal probability plot. This finding is in agreement with the 1993 recommendation from the American Academy of Pediatrics that infants with a low T4 level and a TSH concentration greater than 40 mU/l be considered to have primary hypothyroidism until proven otherwise. The group of infants with TSH less than 50 mU/l have a higher proportion of males and low birthweight infants. For this group, T4 increases with increasing TSH. We find that screening TSH, T4, and birthweight are predictive of follow-up serum TSH level for the cases with TSH > 50 mU/l but not for cases with TSH < 50 mU/l. An optimal rule for selecting screening cutoff levels is presented based on only T4, TSH and their interaction. Adjustments for sex, birthweight or age at which sample was taken did not aid in distinguishing cases from controls for newborns whose age of sample is 2 days or greater.
