RESUMO
Background: Congenital hypothyroidism due to defects in iodotyrosine deiodinase has variable phenotypes and can present as hypothyroid or with normal thyroid testing. Methods: Whole exome sequencing was performed in individuals from two families originating from different regions of Sudan. Mass spectrometry of urine and serum iodotyrosines was performed on subjects from both families. Results: A novel iodotyrosine deiodinase (IYD) mutation (c.835C>T; R279C) was identified in individuals from two Sudanese families inherited as autosomal recessive. The mutation was identified by multiple in silica analyses to likely be detrimental. Serum and urine monoiodotyrosine (MIT) and diiodotyrosine (DIT) were markedly elevated in the homozygous subjects. Conclusion: Measurement of serum and urine DIT and MIT was more sensitive than that of urine iodine or serum thyroid function tests to determine the effect of the IYD mutation.
Assuntos
Hipotireoidismo Congênito , Di-Iodotirosina , Mutação , Humanos , Hipotireoidismo Congênito/genética , Di-Iodotirosina/genética , Iodeto Peroxidase/genética , Monoiodotirosina/genéticaRESUMO
The thyroglobulin (TG) gene encodes a protein required for thyroid hormone synthesis and iodine storage. Deleterious TG mutations produce congenital hypothyroidism (CH) often presenting with undetectable serum TG. Alu elements, common throughout the human genome, have a poly(dA) region in the 3' end of the strand. Herein two of four siblings of a consanguineous Sudanese family with CH, goiter, high initial serum thyrotropin, and undetectable TG were found to have a novel frameshift insertion of an Alu element within an exon of the TG gene: c.7909ins p.Y3637Ffs. This report demonstrates a novel Alu element insertion within TG causing CH.