Variation by ethnicity in the prevalence of congenital hypothyroidism due to thyroid dysgenesis.
BACKGROUND
The scant data on ethnic differences in the prevalence of congenital hypothyroidism (CH) have generally not taken etiology of CH into account. Our hypothesis is that the prevalence of CH due to thyroid dysgenesis (TD) varies by ethnicity.


METHODS
This case-control study included all patients with CH due to TD (a condition of unknown origin) or to dyshormonogenesis (DH, of known autosomal recessive transmission) between 1987 and 2009. Etiology was established by (99m)Tc scintigraphy. The parents self-assessed their ethnicity, which we grouped in Caucasian, Hispanic, black, Asian, and Maghreb/Middle East. We compared ethnicity between the 190 patients with TD (147 ectopies, 40 athyreoses, and 3 orthotopic hypoplasias) and the 44 patients with DH. Ethnicity was also compared to the reference population of the city of Montreal. Prevalence odds ratios (POR) were calculated and compared by the bilateral Fisher's exact test.


RESULTS
The ethnic composition of the DH group was similar to that of the reference population. In blacks, TD prevalence of 1 in 190 (0.5%) was low compared to that of DH (4 in 44; 9.1%; POR 0.06; 95% confidence interval: 0.001-0.56; p = 0.005). In contrast, Caucasians showed an increased TD prevalence of 166 in 190 (87.3%) compared to that of DH (30 in 44; 68.2%; POR 3.21; 95% confidence interval: 1.37-7.34; p = 0.0052). No statistically significant differences were observed between other ethnic groups.


CONCLUSIONS
TD is less prevalent in blacks and more prevalent in Caucasians. Blacks being more genetically diverse, this is an argument for an oligogenic inheritance of susceptibility to TD.
Department of Pediatrics, Endocrinology Service and Research Center, CHU Sainte-Justine, Université de Montréal, Montréal, Canada.
Sophie
S
Stoppa-Vaucher
Guy
G
Van Vliet
Johnny
J
Deladoëy
D000367:Age Factors; D016022:Case-Control Studies; D003409:Congenital Hypothyroidism / Q000453:epidemiology / Q000208:ethnology*; D005006:Ethnicity; D020022:Genetic Predisposition to Disease; D006801:Humans; D007231:Infant, Newborn; D015233:Models, Statistical; D016017:Odds Ratio; D015995:Prevalence; D012016:Reference Values; D012189:Retrospective Studies; D013961:Thyroid Gland / Q000002:abnormalities*; D013974:Thyroxine / Q000097:blood
D013974:Thyroxine