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Maternal Hypothyroidism (maternal + hypothyroidism)

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Medical Sciences	100%

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Maternal hypothyroidism in early and late gestation: effects on neonatal and obstetric outcome

CLINICAL ENDOCRINOLOGY, Issue 5 2005
Iskandar Idris
Summary Background, Maternal hypothyroidism may be associated with a variety of adverse neonatal and obstetric outcomes. Whether these outcomes are affected by maternal thyroid status at initial presentation or in late gestation specifically within a dedicated antenatal endocrine clinic remains unclear. The effects of thyroxine dose requirement during pregnancy and serum concentrations of TSH within such clinic settings are still not known. Objectives, We investigated these outcomes in patients with hypothyroidism during early and late gestation. TSH levels and thyroxine dose requirement during early and late gestation were also evaluated. Methods, We performed a retrospective study of data from 167 pregnancies managed in the antenatal endocrine clinic. Analysis of outcomes was linked to TSH at first presentation and in the third trimester. Outcome variables included: rate of caesarean section, pre-eclampsia, neonatal unit admission, neonatal weight and gestational age. Controlled TSH was defined as mothers with TSH between 0·1 and 2 with normal free thyroid hormone levels. Results, The caesarean section (CS) rates were higher in the study cohort (H) compared with the local (C) rate (H = 28·7%, C = 18%). The higher rate in our patient cohort was not due to a higher rate of emergency section nor to a lower threshold for performing elective caesarean section. The infant birthweight (IBW) from mothers with TSH > 5·5 (H1) and mothers with TSH between 0·1 and 5·5 at presentation (H2) was [median (range)] 3·38 (1·73,4·70) vs. 3·45 (1·36,4·76); P = ns. The prevalence of low-birthweight (LBW) infants (< 2·5 g) in groups H1 and H2 was 15% and 4·8%, respectively [odds ratio (OR) = 3·55, 95% confidence interval (95% CI) = 0·96,10·31]. IBW from mothers with TSH > 2 (H3) and mothers with controlled TSH in the third trimester (H4) were similar [3·38 (1·78,4·4) vs. 3·46 (1·36,4·76); P = ns]. The prevalence of LBW in groups H3 and H4 was 9% and 4·9%, respectively (OR = 1·95, 95% CI = 0·52,7·26). The median thyroxine dose (µg) increased significantly during pregnancy (first trimester: 100; second trimester: 125, P < 0·001; and third trimester: 150, P < 0·001) associated with appropriate suppression of TSH levels in the second and third trimesters. Rates of pre-eclampsia or admissions to neonatal units were negligible. Conclusion, Thyroxine dose requirement increases during pregnancy and thus close monitoring of thyroid function with appropriate adjustment of thyroxine dose to maintain a normal serum TSH level is necessary throughout gestation. Within a joint endocrine,obstetric clinic, maternal hypothyroidism at presentation and in the third trimester may increase the risk of low birthweight and the likelihood for caesarean section. The latter observation was not due to a higher rate of emergency caesarean section nor to a lower threshold for performing elective caesarean section. A larger study with adjustments made for the various confounders is required to confirm this observation. [source]

Timing of Thyroid Hormone Action in the Developing Brain: Clinical Observations and Experimental Findings

JOURNAL OF NEUROENDOCRINOLOGY, Issue 10 2004
R. T. Zoeller
Abstract The original concept of the critical period of thyroid hormone (TH) action on brain development was proposed to identify the postnatal period during which TH supplement must be provided to a child with congenital hypothyroidism to prevent mental retardation. As neuropsychological tools have become more sensitive, it has become apparent that even mild TH insufficiency in humans can produce measurable deficits in very specific neuropsychological functions, and that the specific consequences of TH deficiency depends on the precise developmental timing of the deficiency. Models of maternal hypothyroidism, hypothyroxinaemia and congential hyperthyroidism have provided these insights. If the TH deficiency occurs early in pregnancy, the offspring display problems in visual attention, visual processing (i.e. acuity and strabismus) and gross motor skills. If it occurs later in pregnancy, children are at additional risk of subnormal visual (i.e. contrast sensitivity) and visuospatial skills, as well as slower response speeds and fine motor deficits. Finally, if TH insufficiency occurs after birth, language and memory skills are most predominantly affected. Although the experimental literature lags behind clinical studies in providing a mechanistic explanation for each of these observations, recent studies confirm that the specific action of TH on brain development depends upon developmental timing, and studies informing us about molecular mechanisms of TH action are generating hypotheses concerning possible mechanisms to account for these pleiotropic actions. [source]