Iridic and retinal coloboma associated with prenatal methimazole exposure

Department of Internal Medicine, Keio University, Edo, Tōkyō, Japan
American Journal of Medical Genetics Part A (Impact Factor: 2.05). 12/2005; 139A(2):156-8. DOI: 10.1002/ajmg.a.30917
Source: PubMed
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    ABSTRACT: While methimazole (MMI) is widely used in the therapy for hyperthyroidism, several groups have reported that maternal exposure to MMI results in a variety of congenital anomalies, including choanal and esophageal atresia, iridic and retinal coloboma, and delayed neurodevelopment. Thus, adverse effects of maternal exposure to MMI on fetal development have long been suggested; however, direct evidence for the teratogenicity of MMI has not been presented. Therefore, we studied the effects of MMI on early development by using zebrafish as a model organism. The fertilized eggs of zebrafish were collected immediately after spawning and grown in egg culture water containing MMI at various concentrations. External observation of the embryos revealed that exposure to high concentrations of MMI resulted in loss of pigmentation, hypoplastic hindbrain, turbid tissue in the forebrain, swelling of the notochord, and curly trunk. Furthermore, these effects occurred in a dose-dependent manner. Precise observation of the serial cross-sections of MMI-exposed embryos elucidated delayed development and hypoplasia of the whole brain and spinal cord, narrowing of the pharynx and esophagus, severe disruption of the retina, and aberrant structure of the notochord. These neuronal, pharyngeal, esophageal, and retinal anomalous morphologies have a direct analogy to the congenital anomalies observed in children exposed to MMI in utero. Here, we show the teratogenic effects of MMI on the development of zebrafish and provide the first experimental evidence for the connection between exposure to MMI and human MMI embryopathy.
    Birth Defects Research Part B Developmental and Reproductive Toxicology 06/2013; 98(3). DOI:10.1002/bdrb.21057 · 1.17 Impact Factor
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    ABSTRACT: Ocular coloboma is a developmental anomaly of the eye that results from incomplete closure of the optic fissure, occurring 5-7 weeks post conception. Congenital colobomata are important causes of childhood visual impairment and blindness. This defect typically affects the iris, cornea, ciliary body, zonules, retina, choroid and optic nerve. Colobomata can be seen in isolation and in combination with an impressive number of multisystem disorders. As yet, no effective treatment is available for this condition and management is only supportive. Based upon animal studies of coloboma, mendelian genetic disorders and chromosomal abnormalities, the molecular and genetic mechanisms that regulate optic fissure morphogenesis are now being discovered. Defining the genes and environmental factors involved in coloboma formation will aid in the development of potential therapies for patients with this malformation. This review explores the progress in understanding the clinical and molecular aspects of ocular coloboma.
    Expert Review of Ophthalmology 11/2006; 1(2):209-227. DOI:10.1586/17469899.1.2.209
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    ABSTRACT: Introduction:Hyperthyroidism in pregnant women should be adequately treated to prevent maternal and fetal complications, but teratogenic effects of antithyroid drug (ATD) treatment have been described. Evidence is still lacking in regard to the safety and choice of ATD in early pregnancy.Objective:Our objective was to determine to which degree the use of methimazole (MMI)/carbimazole (CMZ) and propylthiouracil (PTU) in early pregnancy is associated with an increased prevalence of birth defects.Methods:This Danish nationwide register-based cohort study included 817 093 children live-born from 1996 to 2008. Exposure groups were assigned according to maternal ATD use in early pregnancy: PTU (n = 564); MMI/CMZ (n = 1097); MMI/CMZ and PTU (shifted in early pregnancy [n = 159]); no ATD (ATD use, but not in pregnancy [n = 3543]); and nonexposed (never ATD use [n = 811 730]). Multivariate logistic regression was used to estimate adjusted odds ratio (OR) with 95% confidence interval (95% CI) for diagnosis of a birth defect before 2 years of age in exposed versus nonexposed children.Results:The prevalence of birth defects was high in children exposed to ATD in early pregnancy (PTU, 8.0%; MMI/CMZ, 9.1%; MMI/CMZ and PTU, 10.1%; no ATD, 5.4%; nonexposed, 5.7%; P < .001). Both maternal use of MMI/CMZ (adjusted OR = 1.66 [95% CI 1.35-2.04]) and PTU (1.41 [1.03-1.92]) and maternal shift between MMI/CMZ and PTU in early pregnancy (1.82 [1.08-3.07]) were associated with an increased OR of birth defects. MMI/CMZ and PTU were associated with urinary system malformation, and PTU with malformations in the face and neck region. Choanal atresia, esophageal atresia, omphalocele, omphalomesenteric duct anomalies, and aplasia cutis were common in MMI/CMZ-exposed children (combined, adjusted OR = 21.8 [13.4-35.4]).Conclusions:Both MMI/CMZ and PTU were associated with birth defects, but the spectrum of malformations differed. More studies are needed to corroborate results in regard to early pregnancy shift from MMI/CMZ to PTU. New ATD with fewer side effects should be developed.
    The Journal of Clinical Endocrinology and Metabolism 10/2013; 98(11). DOI:10.1210/jc.2013-2831 · 6.31 Impact Factor