[Epidemiologic characteristics and risk factors for congenital hypothyroidism from 1989 to 2014 in Beijing].

OBJECTIVE: To investigate the epidemiologic characteristics and risk factors for congenital hypothyroidism (CH) in Beijing between the years 1989 and 2014.

METHODS: Information on neonatal screening, and diagnoses and treatment of CH from 1989 to 2014 were obtained from the database of the Beijing Neonatal Screening Center. The screening parameter was thyroid-stimulating hormone (thyrotropin; TSH), which was measured by radioimmunoassay (RIA) from 1989 to 1995, enzyme-linked immunosorbent assay (ELISA) from 1996 to 2003, and time-resolved fluorescence immunoassay (DELFIA(®)) from 2004 to 2014. The cutoff value of each screening method was set as the international standard for the corresponding years (20 mIU/L from 1989 to 1995 and 10 mIU/L from 1996 to 2014). CH was diagnosed using "The Technical Specification of Diagnosis and Treatment of Phenylketonuria and Congenital Hypothyroidism" , published in 2010 by the Ministry of Health of the People's Republic of China. Data on live birth infants were obtained from Beijing obstetric quality reports. The incidence of CH using different screening methods was compared, and trends in annual incidence were analyzed. To exclude the influence of different screening methods, data from the years 2004 to 2014 were used to identify the risk factors for CH.

RESULTS: Between 1989 and 2014, the incidence of CH in Beijing was 36.7 per 100 000 individuals, with permanent CH (PCH) and transient CH (TCH) having incidences of 16.4 per 100 000 and 15.9 per 100 000, respectively. The annual incidence of CH increased from 11.2 per 100 000 in 1989 to 51.0 per 100 000 in 2014 (χ(2)=119.02, P<0.001), with PCH increasing from 5.6 to 16.0 per 100 000 (χ(2)=34.38, P<0.001) and TCH increasing from 5.6 to 13.0 per 100 000 (χ(2)=26.93, P<0.001). Among the PCH cases, 70.44% (255/362) were thyroid dysgenesis or ectopic glands, while the other 29.56% (107/362) were dyshormonogenesis. Between 2004 and 2014, the incidence of CH in females (51.7/100 000) was higher than in males (37.0/100 000), and it was higher in post-term (334.5/100 000) and preterm births (77.8/100 000) than that in term births (41.4/100 000). It was also higher in the low birth weight (87.7/100 000) than the normal (42.4/100 000) and high birth weight (42.6/100 000) populations.

CONCLUSIONS: Between 1989 and 2014, there was a tendency towards an increase in the overall incidence of CH, and the incidence of both PCH and TCH in Beijing. Female sex, preterm birth, older gestational age, low birth weight, and preterm birth were risk factors affecting the incidence of CH in Beijing.