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Effect of different starting doses of levothyroxine on growth and intellectual outcome at four years of age in congenital hypothyroidism.

To evaluate the effect of different initial levothyroxine (LT4) replacement doses on growth and intellectual outcome in patients with congenital hypothyroidism (CH) detected by neonatal screening program, the longitudinal growth and intelligence quotient (IQ) were assessed and compared at 4 years of age in 83 patients with CH. The patients were divided into three groups according to the initial LT4 dose used: (1) group 1 (n = 42) received the previously recommended dose of 6.0-8.0 microg/kg per day; (2) group 2 (n = 21) received a dose of 8.1-10.0 microg/kg per day; (3) Group 3 (n = 20) a dose of 10.1-15.0 microg/kg per day. The IQ, evaluated by the Wechsler Preschool and Primary Scale of Intelligence test at 4 years of age, was significantly higher in group 3 (IQ 98 +/- 9) compared to group 1 (IQ 88 +/- 13; p < 0.05) but not compared to group 2 (IQ 94 +/- 13). However, the IQs were below the normal range (< 85) in six patients from group 2 (28%), but in none of the patients from group 3 (p = 0.03). Patients from group 3, with severe CH at diagnosis, had an IQ (97 +/- 9) at 4 years of age, which was not different from that of patients from the same group with moderate CH at diagnosis (IQ 99 +/- 9). Similar results were also observed in patients from group 2 however, mean IQ scores in these patients (93 +/- 12) were several points lower than those observed in patients from group 3 (95 +/- 15). After the first month of treatment, optimal serum levels of thyroxine (T4) and free thyroxine (FT4) were achieved in all groups, however, only patients from group 3 were able to normalize thyrotropin (TSH) (group 1, 16.0 +/- 12.0; group 2, 9.2 +/- 10.0; and group 3, 2.4 +/- 3.3 mU/L; p < 0.0001). Twelve patients from group 2 treated with an initial LT4 dose above 9 microg/kg per day were able to normalize TSH levels within the first 3 months of life and this resulted in a better IQ (97 +/- 16) compared to the remaining patients from the same group (IQ 90 +/- 9). In the whole group of 83 patients the IQ at 4 years of age was positively correlated to both initial LT4 dosage (r = 0.27, p < 0.02) and FT4 concentrations after the first month of treatment (r = 0.29, p < 0.02), and negatively correlated to TSH concentrations after the first month of treatment (r = -0.27, p < 0.02). No significant differences were observed in height, weight, head circumference, and bone age maturation among the three groups of patients. No clinical signs or symptoms of overtreatment were observed during follow-up in patients receiving the higher LT4 dosage. Our results indicate that high LT4 starting doses rapidly normalize serum TSH concentrations resulting in an improvement of the IQ at 4 years of age, even in patients with severe CH at diagnosis. Growth and bone age maturation are not affected by such a high dose.

Body Height↗

The molecular basis of human 3-methylcrotonyl-CoA carboxylase deficiency.

Isolated biotin-resistant 3-methylcrotonyl-CoA carboxylase (MCC) deficiency is an autosomal recessive disorder of leucine catabolism that appears to be the most frequent organic aciduria detected in tandem mass spectrometry-based neonatal screening programs. The phenotype is variable, ranging from neonatal onset with severe neurological involvement to asymptomatic adults. MCC is a heteromeric mitochondrial enzyme composed of biotin-containing alpha subunits and smaller beta subunits. Here, we report cloning of MCCA and MCCB cDNAs and the organization of their structural genes. We show that a series of 14 MCC-deficient probands defines two complementation groups, CG1 and 2, resulting from mutations in MCCB and MCCA, respectively. We identify five MCCA and nine MCCB mutant alleles and show that missense mutations in each result in loss of function.

Alleles↗

Congenital hypothyroidism: diagnosis and management.

Every newborn infant should be screened for congenital hypothyroidism before discharge from the nursery. Neonatal screening for hypothyroidism was introduced to North America in 1972 and has been demonstrated to be cost effective in the prevention of neurological damage in children. Interpretation of diagnostic test results from such programs is based on understanding the physiology of the thyroid gland and recognition that neonatal hypothyroidism primarily stems from an embryological disorder of thyroid development rather than central causes involving the hypothalamic-pituitary axis. Early diagnosis of hypothyroidism is dependent on proper timing and collection of blood samples and an efficient screening program reporting accurate results. A thorough maternal and family history in conjunction with clinical signs and symptoms of hypothyroidism, biochemical tests, and radiological findings should be used to rapidly establish the diagnosis. Early detection and treatment with thyroxine normalizes skeletal maturation, physical growth, cognitive functioning, and motor development of affected newborns. Nurses play an important role in identification, management, and supportive care of infants with hypothyroidism so that maximal potential is achieved.

Clinical Protocols↗

Performance assessment of neonatal dried blood spot testing for HIV antibody.

A study was undertaken to assess the performance of laboratories participating in the UK unlinked anonymised neonatal screening programme for the detection of HIV antibody. A coded panel of 100 contrived dried blood spots prepared form well characterised anti-HIV-1 and anti-HIV-2 positive sera and an anti-HIV negative serum was distributed to eight testing centres. Fifty-one out of 52 anti-HIV-1 positive samples were identified by all eight laboratories: five laboratories identified all 52 specimens. Only one laboratory detected all four anti-HIV-2 positive spots. None of the laboratories reported a seronegative spot as reactive. The sensitivity of anonymised neonatal anti-HIV-1 screening was deemed satisfactory in all participating laboratories but the margin of sensitivity was insufficient to allow pooling of dried blood spot eluates before testing. Technical modifications would be necessary to increase sensitivity for anti-HIV-2 were HIV-2 infection to be reported more frequently in the UK. Performance assessment of the screening programme should be repeated at regular intervals.

AIDS Serodiagnosis↗

Newborn screening of homocystinuria: quantitative analysis of total homocyst(e)ine on dried blood spot by liquid chromatography with fluorimetric detection.

Identification of homocystinuric newborns is hindered by the pitfalls of neonatal screening programs. We propose a fluorimetric HPLC method with a rapid pre-analytical step for homocysteine determination from neonatal dried blood spot cards. Homocysteine in blood spots sampled among 2000 healthy newborns on living day 4, averaged 2.92+/-2.07 microM (range 0.4-7.5). In eight homocystinuric control children, mean values were 61.71+/-52.84 microM (range 18.9-145.7). The method showed a good linearity (r=0.999), precision (RSD<7%) and recovery (95%). The correlation between blood spots and plasma samples was r=0.90. This method has all the essential features for a homocystinuria screening program: an easy and rapid pre-analytical step combined with method linearity and precision.

Amino Acids↗

Children with irreversible brain damage associated with hypothyroidism and multiple intracranial calcifications.

Children who develop clinical hypothyroidism in early childhood have various degrees of irreversible brain damage, albeit less severe than cases detected by neonatal screening test for hypothyroidism in the first months of the life. We report three patients with hypothyroidism of childhood onset after a normal neonatal thyroid-stimulating hormone screening who showed deceleration in linear growth, spasticity in the lower limbs with deformity, mild intellectual impairment, and multiple calcifications in the basal ganglia and subcortical areas. The neurologic symptoms were not progressive but were irreversible in spite of thyroxine treatment. Motor disturbances commonly observed in postnatal-onset hypothyroidism are similar to those of cerebral palsy. Specific distribution of intracranial calcifications may result from metabolic derangement as a result of hypothyroidism, although the mechanism of calcification is not fully understood. We emphasize the need to re-evaluate thyroid function in diplegic patients with specific intracranial calcifications but normal neonatal thyroid-stimulating hormone screening.

Basal Ganglia Diseases↗

[Epidemiological data. Neonatal and prenatal screening].

Unlike what is generally thought, cystic fibrosis is not the most frequent hereditary disease. Its frequency is approximately 1/3 200 and varies with the geographic area. The frequency of heterozygous subjects is about 1/28. No country has established a generalized neonatal screening programme, for technical reasons and because there has been no demonstration of a beneficial effect from early care. It would nevertheless be useful to develop experimental programmes defining which protocols might best be established. Antenatal screening can be based on detecting heterozygous subjects, a technically feasible operation, although answers to a large number of questions would be required.

Cystic Fibrosis↗

A neonatal mass-screening for congenital adrenal hyperplasia in Japan.

A pilot neonatal mass-screening for congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency (21-OHD) was performed in the western region of Shizuoka Prefecture, Japan, using a simplified radioimmunoassay method for 'Disc-17-hydroxyprogesterone (17-OHP) determination. The results obtained during a 30-month period indicated that 3 infants out of the 34314 neonates examined were proved to have 21-OHD, and the incidence of homozygotes and heterozygotes were estimated to be 1:11438 and 1:54, respectively. At the time of recall, the concentrations of plasma 17-OHP and 21-deoxycortisol and their urine metabolites as well as plasma sodium levels were quite applicable to diagnosis, while the clinical signs that may be manifest in 21-OHD were of little value in this connection. Prematurity and perinatal complications of neonates tended to give false-positive results, being secondary to the function of the residual foetal adrenal cortex and non-specific stimulatory effects of various stresses. Despite several technical and practical problems to be solved, the present study demonstrated the importance and validity of a neonatal mass-screening program for CAH.

17-alpha-Hydroxyprogesterone↗

Prevention of intellectual and other disabilities: the Singapore experience.

In Singapore, first level prevention, aimed at reducing the occurrence of disabilities, has included neonatal screening for glucose-6-phosphate dehydrogenase deficiency, a programme of universal vaccination, screening for congenital hypothyroidism, and improvements in obstetric and neonatal care. Non-specific measures, such as improved housing, better nutrition and higher standards of education, have also contributed to the reduction in serious illnesses that can potentially cause disabilities. Second level prevention, designed to limit or reverse a disability, has included a developmental screening programme carried out in the primary health care sector. Centralised multi-disciplinary developmental assessment clinics have been established to define better the disabilities and to advise on rehabilitation. An early intervention programme has been started, and special schools are being upgraded. Third level prevention, aimed at preventing a disability from becoming a handicap, has included the setting up of comprehensive rehabilitation programmes, provision of aids and appliances, vocational training, and job opportunities. The integration of the handicapped back into society is currently being promoted.

Child↗

Blood immunoreactive trypsinogen concentrations are genetically determined in healthy and cystic fibrosis newborns.

Newborns with cystic fibrosis (CF) have increased blood immunoreactive trypsinogen concentrations. When screening for CF in the newborn by immunoreactive trypsinogen measurement, an abnormally high proportion of healthy deltaF508 carriers is found among false-positive neonates, suggesting that a relationship could exist between immunoreactive trypsinogen concentration at birth and the genetic status. Therefore, this study analysed the possible relationships between neonatal blood immunoreactive trypsinogen concentrations and genotype in 1842 healthy newborns and 111 CF patients detected by a neonatal screening programme. A close correlation was found between immunoreactive trypsinogen and deltaF508: the probability of a healthy newborn being a carrier of this mutation increased regularly with the neonatal immunoreactive trypsinogen concentration. In CF patients, there was a significant difference between deltaF508 homozygotes and deltaF508/X (X = other mutation) compound heterozygotes with respect to the mean neonatal blood immunoreactive trypsinogen concentration. CF neonates with two mutations affecting the nucleotide binding domains of the cystic fibrosis transmembrane conductance regulator protein had significantly higher mean immunoreactive trypsinogen concentrations than patients with one mutation affecting a membrane-spanning domain. The data strongly suggest that the neonatal immunoreactive trypsinogen concentration is, in part, genetically determined, with a wide range of variations, similar to the features which have been shown for the relations between the genotype and clinical phenotypes of CF patients.

Case-Control Studies↗

Severe congenital hypothyroidism due to a homozygous mutation of the betaTSH gene.

Isolated TSH deficiency leading to hypothyroidism seems to be a rare condition, escaping the diagnosis by neonatal screening programs, which are based on the primary determination of TSH. This is the first report of a case with an autosomal recessive TSH defect caused by a homozygous mutation of the betaTSH gene that was diagnosed in the early neonatal period. Hypothyroidism in the first child of apparently unrelated parents was suspected because of the classical symptoms of congenital hypothyroidism, which were fully expressed already on the 11th day of life. Routine neonatal TSH-screening on the 4th day of life had been normal, but subsequent determination of serum thyroid hormone levels revealed almost undetectable levels and thyroid hormone substitution was immediately started. Because there was no indication for other pituitary hormone deficiencies, sequence analysis of the betaTSH gene was initiated. A homozygous T deletion in codon 105 was found resulting in a change of a highly conserved cysteine to valine followed by eight altered amino acids and a premature stop codon due to the frame-shift. This altered betaTSH is a biologically inactive peptide. Because of the early development of severe symptoms, it is possible that this altered TSH suppresses the physiologic constitutive activity of the unliganded TSH receptor. Rapid molecular diagnosis in this patient clarified the diagnosis without additional endocrine and imaging studies and it is concluded, that symptoms of hypothyroidism in the neonatal period should result always in an immediate comprehensive work-up of thyroid function including molecular genetic studies irrespective of the screening result.

Congenital Hypothyroidism↗

Screening for cystic fibrosis in newborn infants: results of a pilot programme based on a two tier protocol (IRT/DNA/IRT) in the Italian population.

OBJECTIVE: To assess the performance of a two tier neonatal screening programme (IRT/DNA/IRT) for cystic fibrosis, based on immunoreactive trypsinogen (IRT) followed by direct cystic fibrosis transmembrane conductance regulator (CFTR) gene analysis (based on a panel of up to 31 mutations) in hypertrypsinaemic newborn infants and to compare it with a previous screening protocol. SETTING: The study comprised all the newborn infants in the period 1 October 1998 to 31 December 1999 in the Lombardia region, north western Italy. METHODS: The screening strategy consisted of an immunoreactive trypsinogen assay from dried blood spots, a polymerase chain reaction (PCR) followed by an oligonucleotide ligation assay (PCR-OLA), and a sequence code separation. RESULTS: 104 609 newborn infants were screened. 1457 hypertrypsinaemic infants (1.39%) were analysed with the PCR-OLA assay. 18 newborn homozygotes or compound heterozygotes for CFTR mutations were identified and referred to the cystic fibrosis (CF) centre at a mean age of 3 weeks. 125 infants presenting only one mutation were recalled for a sweat test: a diagnosis of CF was made in 13 infants, and parents of 112 neonates identified as carriers (1:13) received genetic counselling. The remaining 1314 hypertrypsinaemic newborn infants were recalled for IRT retesting and 177 were referred for a sweat test because the second IRT measurement was above the cut off value. Among this group a further two infants were diagnosed with CF (1.1%) leading to a CF prevalence of 1:3170. CONCLUSIONS: This strategy resulted in an early and accurate diagnosis of CF. The IRT/DNA/IRT protocol with an OLA assay was shown to be useful in an Italian population with a genetic heterogeneity, leading to the identification of 94% of infants with CF.

Cystic Fibrosis↗

[Screening of newborn infants for hypothyroidism in Berlin (West) 1978-1982].

In July 1978 a neonatal screening program for congenital hypothyroidism was introduced in Berlin (West) covering more than 98% of the neonates born in the city area. Up to July 1982 TSH was determined on the fifth day of life in 74,350 newborns using a radioimmunoassay for TSH determination in dried blood spots. With a cut-off limit at 20 microU/ml, a control examination was necessary in 0.96% of the newborns. 32 infants with congenital hypothyroidism were detected and treated with 1-thyroxine, giving a total incidence of 1 in 2,323 newborns (permanent and transient cases). 63% of all newborns with elevated TSH levels (greater than 20 microU/ml) were born in the obstetric department of the Neukölln-Hospital, which uses PVP-Iodine for vaginal disinfection of the mothers during labor and delivery, especially after premature rupture of membranes. Those newborns had only transient TSH-elevations, which were normalized on the tenth day of life. The replacement therapy was started on the average on the ninth day of life. The symptoms present in the newborns with congenital hypothyroidism differed from patient to patient and from the "classical" signs of congenital hypothyroidism described in the literature. All infants detected by the screening program are followed in the outpatient department of the Children's Hospital of the Free University in Berlin and show a normal motor and mental development, except for two infants with other causes for retardation in psychomotor development.

Berlin↗

Phenylketonuria screening with a fluorometric microplate assay.

A fluorometric assay in microtitre plates for the screening of phenylketonuria was evaluated and adapted to a neonatal screening programme. Using this assay, it is possible to determine quantitatively the phenylalanine concentration in dried blood spots on filter paper. The test exhibited a linear calibration curve with a good slope as well as sufficient precision and accuracy in the statistical analysis. Interference by other amino acids and antibiotics was not observed. Only elevated concentrations of leucine interfered to a small degree. The phenylalanine concentration in dried blood spots of 13 phenylketonuria patients correlated to that in serum. 7381 dried blood samples of newborn infants were tested simultaneously by both the fluorometric and the Guthrie test. The results did not show significant differences. We screened 29,182 newborns using the fluorometric assay and an online data processing programme. The internal repetition rate was 0.64%, the external recall rate 0.15%. False negative results were not observed. In December 1991 the fluorometric method replaced the Guthrie test in our routine programme for phenylketonuria screening, and was introduced as a follow up test for phenylketonuria patients.

Fluorometry↗

Intraparenchymal hemorrhage in preterm neonates: a broadening spectrum.

Among 800 neonates screened for cerebral bleeding, perinatal sonography identified 35 preterm neonates with intraparenchymal hemorrhage (IPH). The observed IPHs were categorized in five general groups: classical grade-IV hemorrhage (16 patients), grade-IV hemorrhage with coexisting but anatomically separate hemorrhages (four patients), grade-IV hemorrhage with later development of secondary parenchymal hemorrhages at distant sites (five patients), hemorrhagic periventricular leukomalacia (four patients), and parenchymal hemorrhage unrelated to grade-IV hemorrhages (six patients). Thirty IPHs had concurrent germinal matrix hemorrhages, but in only 16 patients did the IPH represent an extension of the subependymal hematoma and therefore qualify as pure grade-IV hemorrhage according to the most popular classification. The high concurrence of periventricular leukomalacia (80-100% in most groups) and germinal-matrix-remote IPHs supports the concept that most IPHs in preterm neonates represent secondary hemorrhages into ischemic brain tissue.

Brain↗