Carlo Corbetta

A 7-year experience with low blood TSH cutoff levels for neonatal screening reveals an unsuspected frequency of congenital hypothyroidism (CH)

Context  The guidelines of the National Academy of Clinical Biochemistry advocated the use of low bloodspot TSH (b‐TSH) threshold for newborn screening of congenital hypothyroidism (CH). The impact generated by the application of this indication is largely unknown.

Neonatal Thyroid Function in Seveso 25 Years after Maternal Exposure to Dioxin

Background Neonatal hypothyroidism has been associated in animal models with maternal exposure to several environmental contaminants; however, evidence for such an association in humans is inconsistent. We evaluated whether maternal exposure to 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), a persistent and widespread toxic environmental contaminant, is associated with modified neonatal thyroid function in a large, highly exposed population in Seveso, Italy. Methods and Findings Between 1994 and 2005, in individuals exposed to TCDD after the 1976 Seveso accident we conducted: (i) a residence-based population study on 1,014 children born to the 1,772 women of reproductive age in the most contaminated zones (A, very high contamination; B, high contamination), and 1,772 age-matched women from the surrounding noncontaminated area (reference); (ii) a biomarker study on 51 mother–child pairs for whom recent maternal plasma dioxin measurements were available. Neonatal blood thyroid-stimulating hormone (b-TSH) was measured on all children. We performed crude and multivariate analyses adjusting for gender, birth weight, birth order, maternal age, hospital, and type of delivery. Mean neonatal b-TSH was 0.98 μU/ml (95% confidence interval [CI] 0.90–1.08) in the reference area (n = 533), 1.35 μU/ml (95% CI 1.22–1.49) in zone B (n = 425), and 1.66 μU/ml (95% CI 1.19–2.31) in zone A (n = 56) (p < 0.001). The proportion of children with b-TSH > 5 μU/ml was 2.8% in the reference area, 4.9% in zone B, and 16.1% in zone A (p < 0.001). Neonatal b-TSH was correlated with current maternal plasma TCDD (n = 51, β = 0.47, p < 0.001) and plasma toxic equivalents of coplanar dioxin-like compounds (n = 51, β = 0.45, p = 0.005). Conclusions Our data indicate that environmental contaminants such as dioxins have a long-lasting capability to modify neonatal thyroid function after the initial exposure.

Congenital hypothyroidism with eutopic thyroid gland: Analysis of clinical and biochemical features at diagnosis and after re-evaluation

CONTEXT In recent years changes in screening strategies for congenital hypothyroidism (CH) led to an increased detection of mild forms of CH, associated with eutopic thyroid gland. OBJECTIVES We aimed to determine the clinical evolution of CH with eutopic thyroid gland and to find out prognostic factors at diagnosis and follow-up. PATIENTS AND METHODS We retrospectively analyzed a group of 84 children with CH and eutopic thyroid gland treated at our institution. They all underwent clinical re-evaluation after the age of 3, based on thyroid function testing after l-thyroxine therapy withdrawal, thyroid ultrasonography, and (123)I scintigraphy with perchlorate discharge test. Genetic analysis was performed in selected cases. RESULTS At re-evaluation, 34.5% of patients showed permanent hypothyroidism and needed l-thyroxine reintroduction, 27.4% had persistent hyperthyrotropinemia (TSH 5-10 mU/L), and 38.1% had transient hypothyroidism. Major risk factors for permanent CH were prematurity, first-degree familial history of goiter/nodules, thyroid hypoplasia at diagnosis, and high l-thyroxine requirements at follow-up. Iodine organification defects were found in 29.7% of patients, 30% of whom harbored DUOX2 mutations. TSH receptor gene mutations were found in 8.7% of patients with persistent thyroid dysfunction and negative perchlorate discharge test. CONCLUSIONS Only one-third of patients with CH and eutopic thyroid gland needed to continue l-thyroxine therapy after re-evaluation. A frequent finding was the persistence of mild hyperthyrotropinemia. The evolution of CH remains difficult to predict, although different clinical features might suggest different outcomes. Mutations in the genes commonly linked to mild forms of CH were documented in a minority of cases.

Congenital Hypothyroidism due to Defects of Thyroid Development and Mild Increase of TSH at Screening: Data From the Italian National Registry of Infants With Congenital Hypothyroidism

CONTEXT Over the years lower TSH cutoffs have been adopted in some screening programs for congenital hypothyroidism (CH) worldwide. This has resulted in a progressive increase in detecting additional mild forms of the disease, essentially with normally located and shaped thyroid. However, the question of whether such additional mild CH cases can benefit from detection by newborn screening and early thyroid hormone treatment is still open. OBJECTIVE The aim of this study was to estimate the frequency of cases with mild increase of TSH at screening in the Italian population of babies with permanent CH and to characterize these babies in terms of diagnosis classification and neonatal features. METHODS Data recorded in the Italian National Registry of infants with CH were analyzed. RESULTS Between 2000 and 2006, 17 of the 25 Italian screening centers adopted a TSH cutoff at screening of <15.0 μU/mL. It was found that 21.6% of babies with permanent CH had TSH at screening of 15.0 μU/mL or less, whereas this percentage was 54% in infants with transient hypothyroidism. Among the babies with permanent CH and mild increase of TSH at screening (≤15 μU/mL), 19.6% had thyroid dysgenesis with serum TSH levels at confirmation of the diagnosis ranging from 9.9 to 708 μU/mL. These babies would have been missed at screening if the cutoff had been higher. CONCLUSIONS Lowering TSH cutoff in our country has enabled us to detect additional cases of permanent CH, a number of which had defects of thyroid development and severe hypothyroidism at confirmation of the diagnosis.

Newborn of mothers affected by autoimmune thyroiditis: the importance of thyroid function monitoring in the first months of life

Backgroundevaluation of thyroid function in neonates born from mothers affected by autoimmune thyroiditis in order to define if a precise follow-up is necessary for these children. The influence of maternal thyroid peroxidase antibody (TPOAb) and L-thyroxine therapy during pregnancy on neonatal thyroid function was also investigated.Methods129 neonates were tested for thyroid function by measurement of free thyroxine (FT4) and thyroid stimulating hormone (TSH) in 3th day, 15th day and at one month of life. TPOAb were measured in all patients; periodical control of thyroid function were performed until 6 months of life if Ab were positive. Data concerning etiology of maternal hypothyroidism and maternal replacement therapy with L-thyroxine during pregnancy were retrospectively collected.Results28% neonates showed at least a mild increase of TSH value at the different determinations. In the majority of them, a spontaneous completely normalisation of TSH value was observed within the first month life. L-thyroxine replacement therapy was started in 3 neonates. TPOAb titer and maternal L-thyroxine replacement therapy were not related to alteration of thyroid hormone function in our study population.Conclusionstransient mild elevation of serum TSH above the normal reference value for age is frequently observed in the first month of life in infants born from mothers affected by autoimmune thyroiditis. Persistent hyperthyrotropinemia requiring replacement therapy is observed in 2.2% of these neonates. According to our experience, follow-up is recommended in these newborns; the most accurate and not invasive way to carefully monitor these infants after neonatal screening for CH seems to be serum-testing TSH between 2ndand 4th week of life.

Congenital hypothyroidism with gland in situ: Diagnostic re-evaluation

In the past, most congenital hypothyroidism (CH) children with thyroid gland in situ were considered to be affected by hormonogenesis defect. Nowadays, the improved sensitivity of neonatal screening, novel insights into the pathogenic mechanisms and the advances of genetic analyses have reopened the discussion about the etiology of CH with thyroid in situ. We report the etiological re-evaluation of 31 children with thyroid in situ, who had been identified by the CH screening program. The purposes of this re-evaluation were: a) to investigate the definitive diagnosis and pathogenetic mechanism of CH with thyroid in situ in eligible children suspected of dyshormonogenetic defect and b) to verify the adequacy of the treatment schedules. Thirty out of 31 children were affected with permanent hypothyroidism and only one child was euthyroid at re-evaluation (transient CH). Thyroid hormone organification defects were present in less than half of the CH patients with thyroid in situ (13/30); a higher prevalence of partial defects of iodine organification than severe or complete forms was found. An inactivating TSH-receptor gene mutation was found in only one patient without iodine organification defect. Some questions remain unanswered concerning the adequacy of the schedules of treatment, particularly about the proper treatment of mild and borderline forms of CH.

A column-switching HPLC-MS/MS method for mucopolysaccharidosis type I analysis in a multiplex assay for the simultaneous newborn screening of six lysosomal storage disorders

Lysosomal storage disorders comprise a group of rare genetic diseases in which a deficit of specific hydrolases leads to the storage of undegraded substrates in lysosomes. Impaired enzyme activities can be assessed by MS/MS quantification of the reaction products obtained after incubation with specific substrates. In this study, a column-switching HPLC-MS/MS method for multiplex screening in dried blood spot of the lysosomal enzymes activities was developed. Mucopolysaccharidosis type I, Fabry, Gaucher, Krabbe, Niemann-Pick A/B and Pompe diseases were simultaneously assayed. Dried blood spots were incubated with substrates and internal standards; thereafter, supernatants were collected with minor manipulations. Samples were injected, trapped into an online perfusion column and, by a six-port valve, switched online through the C18 analytical column to perform separation of metabolites followed by MS/MS analysis. A total of 1136 de-identified newborn screening samples were analyzed to determine references for enzymes activity values. As positive controls, we analyzed dried blood spots from three patients with Pompe, one with Fabry, one with Krabbe disease and two with MPS I, and in all cases the enzyme activities were below the cutoff values measured for newborns, except for an MPS I patient after successful hematopoietic stem cell transplantation.

Common criteria among States for storage and use of dried blood spot specimens after newborn screening

Biological samples collected in biobanks are a resource with significant research potential. The Italian Joint Group CNB - CNBBSV (National Committee of Bioethics - National Committee for Biosecurity, Biotechnologies and Life Sciences) published a document reporting recommendations on storage and use of dried blood spot (DBS) and on the development of a National Network of Regional Newborn Screening Repositories for collection of residual DBS. Several ethical questions (about consent, possible use of genetic information, unanticipated possible usages for research purposes) rise from residual newborn screening specimens collections. Moreover, legal and ethical controversies are accentuated by the conflicts between the interests of sample donors, biobank holders, researchers and the public. To overcome these difficulties the identification of a few criteria for storage and research usage of DBS is crucial.