Thyroid dyshormonogenesis (TDH) is characterized by the defective synthesis of thyroid hormones. We present a patient with congenital hypothyroidism (CH) who presented in newborn screening with elevated serum thyroid-stimulating hormone (TSH), decreased free thyroxine (fT4) and increased thyroglobulin (Tg) concentrations. Ultrasound scan revealed a properly structured thyroid gland. Treatment with L-thyroxine was initiated. At the age of 2 years, thyroxine replacement was stopped. The patient remained untreated until 6 years of age when TSH levels progressively increased and L-thyroxine treatment was restarted at a dose of 12.5 μg/day. Genetic analysis revealed a double heterozygosity for likely pathogenic variants of dual oxidase 2 (DUOX2) and thyroid stimulating hormone receptor (TSHR). Both genes were earlier shown to be associated with CH. In a literature review, our patient was compared to previously published patients with similar clinical characteristics, and a good genotype-phenotype correlation was identified.
Keywords: DUOX2 variant; TSHR variant; congenital hypothyroidism.