The literature shows a correlation between ethnicity and pathogenic variants of the thyroid stimulating hormone receptor (TSHR) gene. Some of these polymorphisms may be risk factors for the development of primary congenital hypothyroidism (PCH). In this study, we investigated the relationship between the frequency of TSHR gene polymorphisms and the genetic influence of African, Amerindian, and European ancestry-informative markers in patients from an Amazonian population in Brazil who were diagnosed with PCH.