Congenital hypothyroidism is a disorder in which babies are born with low thyroid hormone levels, either because the thyroid did not develop properly (thyroid dysgenesis) or because the thyroid has problems in one of the needed steps to make thyroid hormones (thyroid dyshormonogenesis). Congenital hypothyroidism is estimated to occur in 1:1700 newborns in the most recent literature and, if left untreated or if treatment is delayed, it irreversibly affects brain development. Thyroid scintigraphy is a procedure in which a radioactive compound which is taken up by the thyroid gland is used to determine the location of the gland or to confirm the absence of thyroid tissue. This procedure needs to be done when the child is not on thyroid hormone, either prior to starting treatment or after holding treatment for some weeks.
Thyroid ultrasound and thyroid scintigraphy have been used to determine the cause of congenital hypothyroidism, whether due to dyshormonogenesis or dysgenesis. In dysgenesis, the gland may be absent, smaller, or in an abnormal position. In dyshormonogenesis, the gland is usually normal or larger in the absence of thyroid hormone replacement. Thyroid dyshormonogenesis may be inherited in 25% of the children in a family, so it is important to make the right diagnosis of this condition for genetic counseling. Since the outcomes of congenital hypothyroidism depend on starting treatment as soon as possible after diagnosis, diagnostic studies to determine the etiology of congenital hypothyroidism are usually delayed after the age of three years, or not done at all, which may cause uncertainty in the patient and lack of adequate genetic counseling. This study was done to determine whether ultrasound of the thyroid could have a role in the early diagnosis of congenital hypothyroidism and to determine whether delaying ultrasound could provide misleading information.
THE FULL ARTICLE TITLE:
Borges MF et al. Timing of thyroid ultrasonography in the etiological investigation of congenital hypothyroidism. Arch Endocrinol Metab. February 13, 2017 [Epub ahead of print]. doi:10.1590/2359-3997000000239
SUMMARY OF THE STUDY
A total of 44 patients with a diagnosis of congenital hypothyroidism from the state of Minas Gerais, Brazil, were invited to have thyroid US at the Universidade Federal do Triângulo Mineiro in Uberaba, Brazil. All except three accepted the invitation and participated in the study (23 females and 18 males), ranging in age from 0.2 to 45 years. All were receiving treatment and were considered to have congenital hypothyroidism, except for 1 patient, whose elevation in TSH was transient and had resolved. Patients were divided in two groups: Group 1 (23 patients) included patients diagnosed by the State Neonatal Screening program and Group 2 (21 patients) included patients who had been followed in the city of Uberaba’s Municipal Health Unit. In Group 1, 15 patients had already undergone ultrasound and scintigraphy between ages 3 and 4. In Group 2, 15 of the patients had previously undergone ultrasound, but only two had undergone thyroid scintigraphy. Information related to these prior studies was obtained from the medical records. The second ultrasound was compared to the initial one, when available. When a thyroid was found, measurements were obtained to calculate the thyroid volume. The volumes were compared with reference ranges from medical references or from normal children to determine whether glands were bigger, normal or smaller than normal.