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A ten-year temporal analysis of primary congenital hypothyroidism in Israel
I Kaiserman1, R Siebner, G Kletter
1Pediatric Endocrinology, Sheba Medical Center, Tel-Hashomer, Israel.
Insights
This study found no significant seasonal patterns in congenital hypothyroidism (CH) incidence in Israel. Analysis of 10 years of screening data suggests a non-periodic cause for this condition.
Area of Science:
- Endocrinology
- Pediatrics
- Epidemiology
Background:
- Congenital malformations can exhibit seasonal variations, hinting at environmental factors like viral infections.
- Previous research indicated variability in congenital hypothyroidism (CH) incidence rates.
Purpose of the Study:
- To investigate the incidence and potential seasonal variations of congenital hypothyroidism (CH) in Israel.
- To determine if CH has a periodic or non-periodic etiology based on birth data.
Main Methods:
- Screening data for primary CH from 303 infants born in Israel between April 1978 and March 1988.
- Analysis of annual and monthly CH incidence rates.
- Autocorrelation and Fourier analysis of monthly CH incidences and maternal last menstrual periods.
Main Results:
- Overall CH incidence was 1/3192 live births.
- Significant annual variations observed, with low incidence in 1978-1979 and high in 1985.
- No significant periodicity found in monthly CH incidence or maternal last menstrual periods.
Conclusions:
- The etiology of sporadic primary CH in Israel appears to be non-periodic.
- Seasonal factors, if present, do not significantly influence CH incidence in this population.
Abstract:
It was previously shown that some congenital malformations present seasonal variations, suggesting a seasonal etiology such as viral infections. Some earlier studies have shown a certain degree of variation in the incidence rates of congenital hypothyroidism. As from April 1978 all infants born in Israel were screened for congenital hypothyroidism (CH) in one central laboratory at the Sheba Medical Center Tel-Hashomer. During the 10-year screening period (April 1978 to March 1988) 303 infants were found to have primary CH, which constitutes an overall incidence of 1/3192 live births. The annual and monthly birth incidence was calculated for the 120 months of the screening period. The annual CH incidence was significantly low in 1978 and 1979 and significantly high in 1985. There were wide and significant variations in the individual monthly incidences of CH. The average monthly incidence showed a low peak in August; however the autocorrelation analysis of the monthly incidences of CH showed no significant periodicity. This was supported by the Fourier analysis which showed no distinctive frequency peak. The last menstrual period was calculated for 138 of the infants' mothers and an autocorrelation analysis of these dates showed no significant periodicity. These results support a non-periodic etiology for sporadic primary CH in Israel.