Screening for congenital hypothyroidism

Is Umbilical Cord Blood Total Thyroxin Measurement Effective in Newborn Screening for Hypothyroidism?

Objective

To assess the performance of the use of umbilical cord blood for screening of primary congenital hypothyroidism in the Saudi Aramco Medical Services Organization newborn thyroid screening programme.

Methods

Umbilical cord blood total thyroxin (CB-TT4) was measured. In samples with low T4 concentrations, an additional measurement of cord blood thyroid-stimulating hormone was made.

Results

A total of 96,015 newborn infants were screened in the period January 1990-December 2007. Twenty-six cases of primary congenital hypothyroidism, six cases of transient hypothyroidism and 13 cases of central hypothyroidism were detected. This method of screening resulted in 100% sensitivity and 98% specificity (95% CI 84–100, and 95% CI 98–98.2, respectively). However, there was a high mean recall rate of 1.9%.

Conclusion

The use of CB-TT4 is a valid screening strategy for primary congenital hypothyroidism. It meets the metabolic screening demands of early discharge policy and guarantees screening all newborns delivered in the hospital.

Neonatal hyperthyrotropinemia in gestational diabetes mellitus and perinatal complications

The aim of this study is to explore the relationship between high cord blood thyroid-stimulating hormone (TSH) level and in-utero stress to the fetus in gestational diabetes mellitus (GDM). Cord blood TSH results were analyzed in 1,578 euthyroid infants from singleton pregnancies with GDM: 103 with elevated TSH (>16 mIU/l) and 1,475 with normal TSH. Maternal characteristics, pregnancy outcome and perinatal complications were compared between the two groups. Multiple logistic regression was used to study the association between high cord blood TSH level and various perinatal complications which reflect in-utero stress in GDM after adjusting for the confounding effects of parity, instrumental delivery, cesarean section and baby gender. High cord blood TSH level was found to be associated with the 1-min Apgar score <7 (OR 3.31, 95% CI 1.78-6.16), birth trauma (OR 3.44, 95% CI 1.11-10.69), neonatal jaundice requiring treatment (OR 2.08, 95% CI 1.30-3.32), neonatal sepsis (OR 2.34, 95% CI 1.24-4.42), respiratory complications (OR 3.45, 95% CI 1.37-8.70), neurological complications (OR 8.01, 95% CI 1.91-33.60) and overall perinatal morbidity (OR 2.41, 95% CI 1.58-3.67). Cord blood TSH level seems to be a better and independent indicator of the in-utero stress to the fetus in GDM when compared to the commonly used sugar profile result and HbA1c level.

Two years' experience with an enhanced chemiluminescent assay for neonatal blood spot TSH

We have developed a blood spot assay for thyroid stimulating hormone (TSH) based on the Amerlite TSH-30 serum assay for use in the Welsh neonatal hypothyroid screening programme. A total of 67,656 infants were screened in 1994 and 1995, and 28 cases of primary hypothyroidism were detected, giving a prevalence of one in 2416. The method is sensitive and rapid, results being available within 3 h of receipt of samples. The assay enables much faster detection of primary hypothyroidism than was previously possible, and therefore contributes to earlier treatment of affected infants.

Determination of inulin in plasma and urine by reversed-phase high-performance liquid chromatography

We report a new HPLC procedure for measuring inulin in plasma and urine. Samples after dilution are boiled in mild acidic conditions and then analyzed on a C18 column. Solvent system A is 3.2 mM HCl, pH 2.5, and B is acetonitrile-3.2 mM HCl (60:40, v/v), pH 2.5. The separation is carried out in 8 min with a flow-rate of 1.0 ml/min and the absorbance monitored at 280 nm. The relationship between inulin and the recorded peak area is linear from 0.2 to 3.2 mg/ml with a correlation coefficient of 0.999 for plasma and 0.999 for urine. Within-run precision, measured at three inulin concentrations, ranged from 0.9 to 1.7% in plasma and from 0.8 to 1.2% in urine. Between-run precision varied in plasma from 2.7 to 3.2% and in urine from 3.0 to 3.3%. Analytical recovery ranged from 102 to 107% in plasma and from 101 to 105% in urine, respectively. The method is sensitive, selective and only 30-microliters samples are required. Therefore, it could be used to evaluate the glomerular filtration rate even in small babies and to perform studies in animals.

Screening for congenital hypothyroidism in Turkey

A pilot study was performed to determine the incidence of congenital hypothyroidism (CH) in Turkey and to build a model for nationwide screening. From December 1991 to December 1992, 30,097 newborns were screened for CH using a primary measurement of thyroid stimulating hormone in capillary blood on days 3-5 of life. Samples were obtained in collaboration with the ongoing nationwide phenylketonuria screening programme. Eleven cases of primary CH were detected giving the incidence of 1:2736. Recall rate was 2.3%. Replacement therapy with L-thyroxine was started after the confirmation of diagnosis. The median age at the initiation of replacement therapy was 23 days (range 7-35 days).

CONCLUSION

The incidence of CH is notably higher in Turkey than reported in most other countries. Iodine deficiency and/or dyshormonogenesis might contribute to this high incidence. This result emphasizes the necessity of a nationwide screening programme.

Transient neonatal hyperthyrotropinaemia

Of 48 consecutive newborns with elevated umbilical venous plasma thyrotropin (TSH) concentration, only two (4%) were subsequently proved to have congenital hypothyroidism, while the other 46 had transient elevation of TSH. Compared with matched controls, these 46 newborns were all delivered vaginally (P less than 0.0003) and had a longer second stage of labour (P less than 0.002), together with higher incidences of nuchal encirclement of the cord (P less than 0.05) as well as female babies (P less than 0.05). There was no difference in the incidence of antenatal complications, mean gestational age, birth weight, or birth asphyxia. There were no small-for-gestational age infants in the study group, while four were found in the controls. The results indicate that elevated umbilical cord plasma TSH concentration may represent a response to the stress of difficult or complicated delivery in the healthy appropriate- or large-for-gestational age newborn who does not have congenital hypothyroidism.

Influence of mode of delivery on fetal pituitary-thyroid axis

We measured the cord serum levels of thyroid-stimulating hormone (TSH), thyroxine (T4) and triiodothyronine (T3) in 922 neonates delivered by mothers who had no thyroid disorders. The T4 and T3 levels increased progressively from the 27th to the 40th week of gestation. However, the TSH levels varied widely and had no correlation with gestational age, because they were affected by the mode of delivery. The mean cord serum TSH level in neonates delivered by vacuum extraction was 16.3 +/- 10.0 microU/ml (n = 30), which was significantly higher than the level following normal vaginal delivery (9.5 +/- 6.0 microU/ml, n = 622) (p less than 0.005). The mean cord serum TSH level following elective caesarean section was 6.5 +/- 3.1 microU/ml (n = 79), and this was significantly lower than after normal vaginal delivery (p less than 0.005). TSH levels in high-risk neonates were significantly higher than in neonates without risk factors. A significant positive correlation was found between the duration of the second stage of labor and the cord serum TSH level (r = 0.45, n = 412, p less than 0.01). However, there was no correlation between the cord serum TSH level and the congenital hypothyroidism screening TSH level (r = 0.01, n = 468). We conclude that the cord serum TSH level reflects delivery stress and that an elevated level does not influence the congenital hypothyroidism screening TSH test in which blood is obtained at five days of life.

Temporal variations in the ionic transport across rabbit retinal pigment epithelium

The potential difference (PD), short circuit current (SCC) and resistance (R) of rabbit retina-retinal pigment epithelium-choroid-sclera preparations were measured in a modified Ussing chamber. The rabbits were kept in 14 hour light/10 hour dark cycle conditions for 14 days: tissues were taken for measurement at 1.5, 6, 13, 20 and 23 hours after the start of the fifteenth light period. Significant variations in PD and SCC were observed 6 hours into the light cycle while the resistance remained constant during the test period. When in a second experiment the fifteenth light period was replaced by darkness, the highest PD and SCC values recorded occurred 12 hours after the time when the light period should have started in the normal light/dark cycle. In a third experiment the fifteenth light period was replaced by darkness and the retina was removed. There were variations in the PD and SCC as in the second experiment but the SCC peak was reduced in amplitude. From these preliminary studies it is suggested that these variations may be circadian in origin and may be related to variations in retinal function.

Neonatal thyrotrophin and mode of delivery

This study was performed to assess the association between labour and the mode of delivery with the umbilical cord plasma thyroxine (T4) and thyroid-stimulating hormone (TSH) concentrations in full-term uncomplicated pregnancies delivered in our hospital. Babies born vaginally had statistically significantly higher umbilical cord plasma TSH but similar T4 concentrations than babies born by caesarean section. Labour was not associated with either higher TSH or T4 concentrations. All the babies with an elevated TSH concentration (greater than 20 miu/l) were born vaginally. Our findings indicate that the mode of delivery should be taken into consideration in the interpretation of umbilical cord plasma TSH results.