Trends in Incidence Rates of Congenital Hypothyroidism Related to Select Demographic Factors: Data From the United States, California, Massachusetts, New York, and Texas

Abstract

Primary congenital hypothyroidism (CH) is a common and preventable cause of intellectual disability. The incidence rate of CH has been reported to be increasing in the United States, but the factors behind the observed rate increase are not known. We summarize here the data presented at a workshop on CH, at which factors potentially related to the CH-incidence-rate increase (namely, race, ethnicity, sex, and birth outcomes) were evaluated. Data sources for the analyses included a national data set of newborn-screening results and state-specific data from newborn-screening programs in California, Massachusetts, New York, and Texas. The incidence rate of CH increased in the United States by 3% per year; however, an increase did not occur in all states, at a constant rate, or even at the same rate. Analysis of US data (1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000) showed a CH-incidence-rate increase only among white newborns. More recently, in California (2000-2007, the rate was constant in non-Hispanic newborns, but it increased among Hispanic newborns. In the national data, the CH-incidence rate increased similarly among boys and girls, whereas in Texas (1992Texas ( -2006, the rate among boys increased significantly more than among girls and varied according to race and ethnicity. In Massachusetts (1995Massachusetts ( -2007, low birth weight newborns or newborns who had a delayed rise in thyrotropin concentration accounted for the majority of the recent rate increase. Race, ethnicity, sex, and pregnancy outcomes have affected the observed increasing incidence rate of CH, although there have been some inconsistencies and regional differences. The association with preterm birth or low birth weight could reflect the misclassification of some cases of transient hypothyroxinemia as true CH. Future studies of risk factors should focus on correct initial identification and reporting of demographic characteristics and pregnancy outcomes for cases of CH. In addition, long-term follow-up data of presumed cases of CH should be ascertained to differentiate true cases of CH from cases of transient hypothyroidism.

Prevalence of Congenital Hypothyroidism—Current Trends and Future Directions: Workshop Summary

“…Updated data from New York presented at the workshop showed a persistent increase, as in the original publication that stimulated the meeting. 1 Hinton et al 19 incorporate detailed information from the presentations of data from New York, California, Massachusetts, and Texas. A common but not universal pattern in these data was periods of increase with intervals of stable incidence rates.…”

Transient neonatal hyperthyrotropinemia is a risk factor for developing persistent hyperthyrotropinemia in childhood with repercussion on developmental status

“…In the latter, the expected incidence is higher. Confirmed congenital hypothyroidism (CH) occurs in one out of 3500-4000 live births, with a ratio of TNH/CH equal to 0.17/1, but the reported incidence indicates a broad variation between geographical areas and countries, due in part to disagreement in TNH/CH definitions (in Argentina, the incidence has changed from one out of 3108 with a 15 mU/l cutoff to one out of 2367 with a 10 mU/l cutoff) (4), analytical variability of screenings, population genetics, and ethnicity (5). TNH should be differentiated from a false-positive screening test, defined as an abnormal screening test value, with normal results of serum tests taken immediately afterward.…”

Birth prevalence of disorders detectable through newborn screening by race/ethnicity

“…Only limited race-specific disorder profiles have been reported elsewhere. Previous research has examined the relationship between ethnicity and a single genetic disorder, including the prevalence of a mutation or disorder within a specific ethnic group, [4][5][6][7][8] within several ethnic groups in a region, [9][10][11][12][13][14][15][16][17] or by geographic region only. 18,19 No studies have published the disorder prevalence rates by specific racial/ethnicity groups in a large US population.…”