Objective: To identify risk factors for permanent and transient congenital hypothyroidism (CH). Design: A population-based case-control study was carried out by using the network created in Italy for the National Register of Infants with CH. Methods: Four controls were enrolled for each new CH infant; 173 cases and 690 controls were enrolled in 4 years. In order to distinguish among risk factors for permanent and transient CH, diagnosis was re-evaluated 3 years after enrolment when there was a suspicion of transient CH being present. Familial, maternal, neonatal and environmental influences were investigated. Results: An increased risk for permanent CH was detected in twins by a multivariate analysis (odds ratio (OR) ¼ 12.2, 95% confidence interval (CI): 2.4 -62.3). A statistically significant association with additional birth defects, female gender and gestational age .40 weeks was also confirmed. Although not significant, an increased risk of CH was observed among infants with a family history of thyroid diseases among parents (OR ¼ 1.9, 95% CI: 0.7-5.2). Maternal diabetes was also found to be slightly associated with permanent CH (OR ¼ 15.7, 95% CI: 0.9-523) in infants who were large for gestational age. With regard to transient CH, intrauterine growth retardation and preterm delivery were independent risk factors for this form of CH. Conclusion: This study showed that many risk factors contribute to the aetiology of CH. In particular, our results suggested a multifactorial origin of CH in which genetic and environmental factors play a role in the development of the disease. 153 765-773
European Journal of Endocrinology
In the last decade a high frequency of other congenital anomalies has been reported in infants with congenital hypothyroidism (CH) detected by neonatal screening. In the present study the occurrence of additional congenital malformations (CM) in the population of CH infants detected in Italy between 1991 and 1998 (n = 1420) was investigated. In Italy all of the centers in charge of screening, treatment, and follow-up of CH adhere to the Italian National Registry of infants with CH. In this study a high prevalence of additional CM (8.4%), more than 4-fold higher than that reported in the Italian population (1-2%), was found in the population of CH infants. Cardiac anomalies represented the most frequent malformations associated with CH, with a prevalence of 5.5%. However, a significant association between CH and anomalies of nervous system, eyes, and multiple CM was also observed. In conclusion, the significantly higher frequency of extrathyroidal congenital malformations reported in the CH infants than in the general population represents a further argument supporting the role of a genetic component in the etiology of CH. Investigations of the molecular mechanisms underlying developmental events of formation of thyroid and other organs represent critical steps in the knowledge of CH etiology.
Background/Aims: Over the years a rise in the incidence of congenital hypothyroidism (CH) has been described worldwide. The aim of our study was to investigate trends in the incidence of CH in Italy over the period 1987-2008, and to investigate which factors may have influenced the CH incidence in our country. Methods: Data were derived from the Italian National Registry of Infants with Congenital Hypothyroidism. Since 1998 the laboratory procedures related to neonatal screening for CH have changed drastically. Accordingly, we estimated the CH incidence during the period 1987-1998 (period 1) and the period 1999-2008 (period 2). Results: The incidence of CH confirmed at birth (including transient hypothyroidism) has increased from 1:3,000 liveborn infants in period 1 to 1:1,940 in period 2 (+54%), whereas the incidence of purely permanent CH increased from 1:3,200 to 1:2,320 (+38%). Lowering of the TSH cutoff was the most important factor contributing to the increase of CH incidence in Italy. Moreover, an increment of 58% of preterm babies with permanent CH was found in period 2 compared with period 1. Conclusion: Our results suggest that more than one cause is responsible for the rise in the increasing CH incidence, with lowering of the screening TSH cutoff and an increased survival rate of a growing number of preterm babies both playing an important role.
The high CH incidence observed in twins is worthy of interest for the high number of induced pregnancies in Italy as well as in other Western countries. Moreover, the low concordance rate for CH among twins together with a high recurrence risk for the disease among siblings indicates that environmental risk factors may act as a trigger on a susceptible genetic background in the etiology of the disease.
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