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Eltom
Thyroid function in the newborn in relation to maternal thyroid status during labour in a mild iodine deficiency endemic area in Sudan.Eltom A, Eltom M, Idris M, Gebre-Medhin M. Clin Endocrinol (Oxf). 2001 Oct;55(4):485-90. [abstract only]
"OBJECTIVES: Data on neonatal and maternal thyroid function during labour in a mild iodine deficiency endemic area are lacking. The current study focuses on elucidating the thyroid function during labour, in a group of pregnant women who live in an area of mild iodine deficiency in Sudan compared to that observed in their corresponding newborns.
MEASUREMENTS: Serum concentrations of TSH, thyroglobulin (Tg), triiodothyronine (T3) and free thyroxine (FT4) were investigated during labour in a group of mothers and their neonates residing in an area with mild iodine deficiency in Sudan (n = 76 mother-newborn pairs). DESIGN: Maternal blood samples were taken on two occasions: first, during the third trimester of pregnancy (weeks 32-39); and, second, just before delivery. Cord blood samples were obtained by a doctor or a trained midwife during delivery.
RESULTS: The median concentrations (and interquartile ranges) of neonatal TSH, Tg, T3 and FT4 were 6.8 (4.7-12.4) mU/l, 61 (40.2-98.2) microg/l, 0.9 (0.8-1.2) nmol/l and 14.2 (13.4-15.9) pmol/l, respectively. The corresponding levels for the mothers during labour were 2.3 (1.9-3.2) mU/l, 33 (15.0-56.8) microg/l, 2.6 (2.0-2.9) nmol/l and 11.4 (10.3-13.3) pmol/l, respectively. The median neonatal serum concentrations of TSH, Tg and FT4 were significantly higher than the corresponding maternal levels (P < 0.0001, P < 0.0001, P < 0.0001, respectively). In contrast, the median maternal serum concentration of T3 was significantly higher than that of the neonates (P < 0.0001). When the different neonatal thyroid parameters were compared with each other, significant correlations were observed between TSH and FT4 (r = 0.4, P = 0.001); Tg and T3 (r = -0.3, P = 0.04) and Tg and FT4 (r = 0.5, P = 0.0001). Women with Tg concentrations above 20 microg/l showed a higher median TSH concentration and lower median FT4 concentration than those with Tg concentrations below 20 microg/l (P < 0.001, P < 0.001, respectively). Nevertheless, the thyroid function of neonates born of mothers with elevated Tg was similar to that of neonates born of mothers with low Tg levels. No significant changes had occurred in the thyroid function parameters between the third trimester of pregnancy and during the time of labour. The thyroid function indicators of the babies born by vaginal delivery did not differ significantly from those of the babies born by Caesarian section.
CONCLUSIONS: The study suggests that, in areas with mild iodine deficiency, neonates may be at the limit of decompensation as evidenced by their enhanced TSH and Tg levels as well as increased T4 compared to their mothers. This finding must not create a false sense of well-being and points rather to the urgency of iodine supplementation of mothers even in areas with mild iodine deficiency, as in this part of Sudan. The mode of delivery, whether by spontaneous vaginal delivery or Caesarian section, did not seem to affect the thyroid function of the newborn."
Changes in iodine metabolism during late pregnancy and lactation: a longitudinal study among Sudanese women.Eltom A, Eltom M, Elnagar B, Elbagir M, Gebre-Medhin M. Eur J Clin Nutr. 2000 May;54(5):429-33. [abstract only]
"OBJECTIVE: To elucidate the persistence, or otherwise, of the pregnancy-related changes in the iodine metabolism and thyroid function in a population residing in an area of mild iodine deficiency in the Sudan.
DESIGN: A longitudinal prospective cohort study involving pregnant women who were recruited during their third trimester of pregnancy and were followed up for up to nine months after delivery. SETTING: The study was conducted among Sudanese women residing in the Omdurman area in Khartoum, an area with a total goitre rate of 17.5%. Subjects: Forty-seven pregnant women were recruited during their third trimester of pregnancy. Their mean age and weight were 29+/-4.6 y and 62.4+/-8.7 kg, respectively. Age matched healthy non-pregnant women living in the same area (n=40) served as a control group. METHODS: Serum levels of thyrotropin (TSH), thyroxine (T4), triiodothyronine (T3), thyroglobulin (Tg) and the urinary iodine concentration (UIC) were determined during the third trimester (first occasion), and subsequently at three months (second occasion), six months (third occasion) and nine months after delivery (fourth occasion). Control subjects provided corresponding samples on one occasion. Main outcomes measures: UIC, TSH, Tg, FT4 and T3.
RESULTS: During the third trimester of pregnancy the median UIC and the free T4 (FT4) were lower than in the control group (P<0. 0001, P<0.0001, respectively), while the median Tg was higher than in the controls (P<0.03). Three months post-partum maximum thyroidal stimulation was evident, with elevated serum levels of TSH and Tg (P<0.0001, P<0.03) and reduced UIC and serum T3 and FT4 (P<0.0004, P<0.0005, P<0.0001), compared with the control group. Nine months post-partum the thyroid function was restored to the pre-pregnancy state, and the median values of TSH, Tg, T3, FT4 and UIC did not differ significantly from those in the control group.
CONCLUSIONS: Our study suggests that the reversibility of the pregnancy-induced changes in the iodine status and thyroid function to the pre-pregnancy levels may depend on the iodine status of the mother during and after pregnancy. The thyroidal stress during the first three months of the post-partum period, which is partially due to the iodine loss in the breast milk, justifies further detailed studies to assess the iodine content of the breast milk and the role of breast milk as a vehicle for iodine supply of infants in situations of iodine deficiency."
Thyroglobulin in serum as an indicator of iodine status during pregnancy.Eltom A, Elnagar B, Elbagir M, Gebre-Medhin M. Scand J Clin Lab Invest. 2000 Feb;60(1):1-7. [abstract only]
"Serum thyroglobulin and thyrotropin as well as urinary iodine concentrations were measured in healthy, pregnant Swedish (n=27) and Sudanese (n=21) women and the results compared with those of healthy Swedish (n=14) and Sudanese (n=20) non-pregnant controls. The median thyroglobulin concentrations (and interquartile range) in the Swedish pregnant women for the three trimesters were 15.5 (8-24), 10.5 (7-19) and 18.0 (13-25) microg/L, respectively. The median third trimester concentration was higher than both the first and second trimester concentrations, respectively (p<0.0001, p<0.0001). Compared to the control group, the Swedish pregnant women had a significantly higher median thyroglobulin concentration in the third trimester (p<0.05). Among the Sudanese pregnant women, the median serum thyroglobulin concentrations (and interquartile range) were 27.5 (12-40), 25.0 (15-43) and 30.0 (15-67) microg/L during the first, second and third trimesters, respectively. There were no significant differences between these concentrations. Compared to the control group, the Sudanese pregnant women had a significantly higher median thyroglobulin in the third trimester (p<0.01). The Sudanese pregnant women also showed significantly higher median thyroglobulin concentrations than the Swedish pregnant women in all the three trimesters of pregnancy (p<0.05, p<0.001 and p<0.01, respectively). However, there were no significant differences between the two non-pregnant controls. Among the Swedish pregnant women, 40%, 23% and 30% of the subjects showed serum thyroglobulin concentrations above 20 microg/ L during the first, second and third trimesters of pregnancy, respectively. Corresponding figures for the Sudanese pregnant women were 55%, 61% and 64%, respectively. A significantly negative correlation was shown between serum thyroglobulin and urinary iodine concentrations during the second and third trimesters in the Swedish women (r= -0.8, p=0.01 and r= -0.5, p=0.03, respectively), and in the third trimester in the Sudanese women (r= -0.6, p=0.03). No such correlation was observed between thyrotropin and urinary iodine concentration in either the Swedish or the Sudanese pregnant women.
"It is concluded that serum thyroglobulin is a
more sensitive indicator of iodine deficiency than serum thyrotropin
during pregnancy."
Thyroid hormones and iodine status in Sudanese pregnant women with goitre.Eltom A, Elnagar B, Gebre-Medhin M. Int J Food Sci Nutr. 1999 Mar;50(2):105-9. [abstract only]
"Thyroid hormones in relation to iodine status were studied in a group of Sudanese pregnant women with goitre (n = 66). These women were compared with a healthy, non-pregnant control group from the same area (n = 40). Twenty-four-hour urine samples and serum samples were collected during weeks 10-13, 20-24 and 32-39 of pregnancy. The goitrous group had a significantly lower mean urinary iodine concentration (UIC) than the non-pregnant group during weeks 20-24 and 32-39 (P < 0.003 and P < 0.001), respectively. The thyroid-stimulating hormone (TSH) and T3 levels in the pregnant group showed a stable pattern with the progression of pregnancy. TSH values in all the pregnant women were within the reference range. The mean FT4 levels of the goitrous pregnant group, in weeks 20-24 and 32-39 of pregnancy, were significantly lower than that of the non-pregnant control group (P < 0.003 and P < 0.05), respectively. The proportions of the pregnant women with FT4 below the reference range were 31, 50 and 40% in weeks 10-13, 20-24 and 32-39 of pregnancy, respectively. There was no correlation between UIC and TSH, UIC and FT4 and between TSH and FT4 during pregnancy.
"By virtue of the proportion of subjects falling
below and above the reference range, this study indicates that in this
particular study area, UIC and FT4 are better indicators of iodine
status than TSH."
Iodine status, thyroid function and pregnancy: study of Swedish and Sudanese women.Elnagar B, Eltom A, Wide L, Gebre-Medhin M, Karlsson FA. Eur J Clin Nutr. 1998 May;52(5):351-5. [abstract only]
"OBJECTIVE: To examine and compare the effects of pregnancy on the thyroid hormone homeostasis in two different populations with variable iodine supply.
DESIGN: A longitudinal prospective cohort study throughout pregnancy involving Swedish and Sudanese pregnant women. SETTING: The subjects were enrolled consecutively during their antenatal follow-up at health centres at Nyby in Uppsala, Sweden and Omdurman in Sudan. SUBJECTS: Fifty-one apparently healthy women from Uppsala, Sweden and twenty-eight pregnant women from Omdurman, Sudan were recruited during pregnancy. The mean age and weight of the Swedish women at the beginning of pregnancy were 29.9+/-5.4 y and 66.3+/-12.9 kg respectively. The corresponding figures for the Sudanese women were 28.0+/-4.9 y and 64.8+/-9.4 kg respectively. METHODS: Blood samples were drawn on four occasions from the Swedish group at 11-13, 24, 32, and 38 weeks of pregnancy, and on three occasions from the Sudanese group at 10-12, 20-24, and 36-39 weeks. Twenty-four hour urine samples were collected from the same subjects and on the same occasions as blood sampling. The urine samples were kept in a refrigerator until the volumes were measured, after which 20 mL aliquots were taken and kept frozen until analysed. MAIN OUTCOME MEASURES: Twenty-four hour urinary iodine output, TSH, FT4 and T3.
RESULTS: The 24 h urinary iodine output at the different times during gestation were higher among the Swedish women, with mean values (95% confidence interval) of 1.40 (1.19-1.61), 1.33 (1.14-1.51), 1.45 (1.06-1.84) and 1.14 (0.88-1.39) micromol/d, than among the Sudanese cohort, with corresponding values of 0.49 (0.27-0.72), 0.29 (0.19-0.39), 0.56 (0.25-0.88) micromol/d. No significant changes in daily urinary iodine loss were observed in the two groups with progression of pregnancy. However, in the Swedish women the mean free T4 concentration fell from 11.81 pmol/l at the beginning of pregnancy to 8.82 pmol/l and the mean TSH rose from 1.11-1.95 mU/I between the beginning and end of pregnancy. Such changes were not detected among the Sudanese women, who had significantly lower mean TSH values than the Swedish women in weeks 36-39 of pregnancy (P < 0.02), and significantly higher FT4 values than the Swedish women both in weeks 20-24 and in weeks 36-39 (P < 0.005 and P < 0.001) respectively.
CONCLUSIONS: The study suggests that determination of urinary iodine alone gives inadequate information about the capacity of an individual to utilize an available iodine supply and it also shows the existence of different patterns of thyroid response during pregnancy. The history of iodine availability prior to and during pregnancy seems to be an important determinant of the mechanism of thyroid gland response to ensure the extra iodine needed by the growing fetus."
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