potassium-perchlorate and Congenital-Hypothyroidism

At the molecular level, the uptake of radioiodine and pertechnetate is proportional to the expression of the thyroidal sodium/iodine symporter (NIS). Qualitative and quantitative scintigraphic evaluation of the thyroid is performed with a gamma camera fitted with an on-line computer system and enables determination of the iodine uptake or the technetium uptake (TCTU) as an iodine clearance equivalent. Despite new molecular genetic insights into congenital hypothyroidism, the iodine-123 or pertechnetate scan remains the most accurate test for the detection of ectopic thyroid tissue. Following the identification of specific mutations of the genes coding for the NIS, thyroid peroxidase and pendrin, the discharge test has lost its role in establishing the diagnosis of inherited dyshormonogenesis, but it is still of value in the assessment of defect severity. In PDS mutations the test can be used to establish the diagnosis of syndromic disease. Quantitative pertechnetate scintigraphy is the most sensitive and specific technique for the diagnosis and quantification of thyroid autonomy. The method has proved to be valuable in risk stratification of spontaneous or iodine-induced hyperthyroidism, in the estimation of the target volume prior to radioiodine therapy and in the evaluation of therapeutic success after definitive treatment. In iodine deficiency areas the thyroid scan remains indispensable for the functional characterisation of a thyroid nodule and is still a first-line diagnostic procedure in cases of suspected thyroid malignancy. This is especially of importance in patients with Graves' disease, among whom a relatively high prevalence of cancer has been found in cold thyroid nodules. While determination of the TCTU is without any value in the differentiation between autoimmune thyroiditis and Graves' disease in most cases, it is of substantial importance in the differentiation between hyperthyroid autoimmune thyroiditis and Graves' disease.

Topics: Adult; Child; Congenital Hypothyroidism; Gamma Cameras; Humans; Iodine Radioisotopes; Ion Channels; Ion Transport; Perchlorates; Potassium Compounds; Prognosis; Radionuclide Imaging; Radiopharmaceuticals; Sodium Pertechnetate Tc 99m; Symporters; Thyroid Diseases; Thyroid Function Tests; Thyroid Gland; Thyroid Neoplasms; Thyroid Nodule; Thyroiditis, Autoimmune; Ultrasonography

Mutations of the thyroperoxidase (TPO) gene have been reported as being the most severe and frequent abnormality in thyroid iodide organification defect (IOD) causing goitrous congenital hypothyroidism. The objective of this study was to screen and subsequently identify TPO gene mutations in patients with congenital hypothyroidism with evidence of total iodine organification defects (TIOD) or partial iodine organification defect (PIOD) as defined by the perchlorate discharge test. Seven goitrous patients with TIOD and seven patients with PIOD, from three and five unrelated families, respectively, were studied. We were able to detect different TPO genes mutations in patients with TIOD and PIOD. In TIOD families the results were as follows: (1) a homozygous GGCC insertion at exon 8, position 1277 (family 1); (2) compound heterozygosity with a GGCC insertion at exon 8 (1277) and a nucleotide substitution in exon 11 (2068G>C) (family 2); (3) compound heterozygosity with the mutation 2068G>C in exon 11 and a C insertion in exon 14 between positions 2505-2511 (family 3). In patients with PIOD we have detected: (1) only one heterozygous mutation in two families (4 and 5), in exons 11 and 10 (2084G>A and 1780C>A); (2) a compound heterozygous condition in one family (family 6), with mutations, respectively in exons 8 and 10 (1242G>T and 1780C>A); (3) only polymorphisms (family VII) and (4) a heterozygous mutation in the first base of the border exon/intron 9 +1G>T (family VIII). We did not detect inactivating mutations in exons 11, 16, and 21 of the THOX2 gene where mutations have been previously described. We concluded that homozygous and compound heterozygous mutations found in TIOD characterized the autosomal recessive mode of inheritance and will translate a nonfunctional protein or a protein that may not reach the apical membrane. As for PIOD, the majority of the studied kindreds had only heterozygous mutations and/or polymorphisms. It is conceivable that these TPO gene sequence alterations may partially affect the functional state of the translated protein or affect its transport to the apical membrane.

Topics: Adolescent; Adult; Base Sequence; Congenital Hypothyroidism; DNA Transposable Elements; Dual Oxidases; Flavoproteins; Genes, Recessive; Genetic Testing; Goiter; Heterozygote; Homozygote; Humans; Hypothyroidism; Iodide Peroxidase; Iodides; Mutation; NADPH Oxidases; Perchlorates; Polymorphism, Genetic; Potassium Compounds; Thyroid Gland

Thyroid gland ectopy is the most common cause in infants with congenital hypothyroidism (CH). Its association with iodine organification defect, as suggested by positive perchlorate discharge test (PDT) has been reported. However, whether such an association represents a true or transient defect has not yet been determined. This finding has an important clinical, epidemiological, and genetic implications.. To determine the natural history of iodine organification defect in patients with CH caused by thyroid ectopy detected by neonatal screening.. Prospective longitudinal study.. King Khalid University Hospital, Riyadh, Saudi Arabia.. PDT was performed, at the time of diagnosis and follow-up, in infants who showed an enlarged ectopic thyroid gland with a Tc-99m pertechnetate uptake of 2% or more.. Of 115 neonates with ectopic thyroid glands, 19 showed an enlarged gland with Tc-99m uptake ranging from 2 to 3.2%. Perchlorate discharge test was performed in 13 of these and was consistent with iodine organification defect in nine. Repeated PDT in seven patients showed normal values.. The results of the authors' study indicate the transient nature of the iodine organification defect and suggest that a delay in the developmental of synthetic mechanisms occur in the dysgenetic glands.

Topics: Choristoma; Congenital Hypothyroidism; Female; Humans; Hypothyroidism; Infant, Newborn; Male; Neonatal Screening; Perchlorates; Potassium Compounds; Prospective Studies; Radionuclide Imaging; Sodium Pertechnetate Tc 99m; Thyroid Function Tests; Thyroid Gland; Tongue Diseases

Forty children suffering from congenital primary permanent hypothyroidism were studied to determine the diagnostic impact of 123I scintigraphy in comparison to laboratory findings and ultrasonography.. In all patients 123I scintigraphy was performed after intravenous administration of 3.7 MBq 123I. If accumulation of the radiotracer in thyroid tissue occurred a perchlorate discharge test was performed subsequently.. Scintigraphy revealed athyrosis in 7 children. In 11 children a lingual thyroid was observed. Deficiency in iodine organification was diagnosed by a significant discharge of 123I in 15 patients. In four of these children the diagnosis of Pendred's syndrome could be established. Ectopic thyroid tissue could be demonstrated only by scintigraphy where clinical examination and sonography failed in the diagnosis in all cases. Hypoplasia of the thyroid gland as it was diagnosed in 2 cases by ultrasonography appeared to be unlikely because a normal 123I uptake was seen in these patients. In 2 patients with scintigraphic proven athyrosis an orthotopic gland had been considered by ultrasound. In 50% of our patients the final diagnosis could only be established if 123I scintigraphy and perchlorate discharge test were performed.. This findings suggest that scintigraphy is indispensible in the correct diagnostic work up of congenital hypothyroidism.

Topics: Child; Child, Preschool; Congenital Hypothyroidism; Female; Humans; Hypothyroidism; Iodine Radioisotopes; Male; Perchlorates; Potassium Compounds; Radionuclide Imaging; Retrospective Studies; Thyroid Gland; Ultrasonography

Quantitative thyroid scanning using low doses of technetium-99m sodium pertechnetate was performed on 147 infants (55 males and 92 females) with congenital hypothyroidism detected through the national neonatal screening programme. Thirty-two (21.8%) were athyrotic, while 62 (42.2%) had an ectopic thyroid and 53 (36%) had a eutopic gland with increased 99mTc uptake (mean 17%; range, 5%-38%). The perchlorate discharge test (PDT) was performed in nine of the infants with ectopic glands and 15 with eutopic glands; the findings were consistent with an organification defect in 22 cases (seven ectopic and 15 eutopic). Thyroid scintigraphy and PDT can add useful aetiological, genetic and prognostic information in the clinical evaluation of infants with congenital hypothyroidism detected by neonatal screening.

Topics: Choristoma; Congenital Hypothyroidism; Female; Humans; Hypothyroidism; Infant, Newborn; Iodine Radioisotopes; Male; Neonatal Screening; Perchlorates; Potassium Compounds; Radionuclide Imaging; Sodium Pertechnetate Tc 99m; Thyroid Function Tests; Thyroid Gland