Document Detail


Type II and type III deiodinase activity in human placenta as a function of gestational age.
MedLine Citation:
PMID:  8964844     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Thyroid hormones are essential for fetal development. T4 can be activated by type I (ID-I) and type II (ID-II) iodothyronine deiodinase or inactivated by type III deiodinase (ID-III). The influence of placental ID-II and ID-III on the regulation of fetal thyroid hormone levels was investigated. Using [125I]T4 and [125I]T3, respectively, ID-II and ID-III activities were measured in homogenates of normal human placentas from 6-43 weeks gestational age and in placentas from five term neonates with a total thyroid hormone synthesis defect. ID-II and ID-III activities related to protein or DNA concentration decreased and total placental ID-III activity increased significantly during pregnancy, whereas the increase in total placental ID-II activity was not significant. Absolute placental ID-II activity was approximately 200 times lower than ID-III activity at all gestational ages. Therefore, fluctuations in ID-II activity were not likely to have a significant influence on fetal thyroid hormone concentrations, but may play a role in the regulation of intraplacental T3 generation. The high ID-III activity most likely influences the thyroid hormone economy of the fetus. Severely hypothyroid newborns showed strongly decreased serum T4 levels, but serum T3 and placental ID-III activities were similar to those in euthyroid newborns. These results suggest that placental ID-III activity is regulated by serum T3, but not by serum T4.
Authors:
J M Koopdonk-Kool; J J de Vijlder; G J Veenboer; C Ris-Stalpers; J H Kok; T Vulsma; K Boer; T J Visser
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of clinical endocrinology and metabolism     Volume:  81     ISSN:  0021-972X     ISO Abbreviation:  J. Clin. Endocrinol. Metab.     Publication Date:  1996 Jun 
Date Detail:
Created Date:  1996-12-11     Completed Date:  1996-12-11     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0375362     Medline TA:  J Clin Endocrinol Metab     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  2154-8     Citation Subset:  AIM; IM    
Affiliation:
Department of Pediatrics and Neonatology, Academic Medical Center, University of Amsterdam, The Netherlands.
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MeSH Terms
Descriptor/Qualifier:
Female
Fetal Diseases / enzymology
Gestational Age*
Humans
Hypothyroidism / enzymology
Iodide Peroxidase / metabolism*
Isoenzymes / metabolism*
Placenta / enzymology*
Pregnancy
Chemical
Reg. No./Substance:
0/Isoenzymes; EC 1.11.1.8/Iodide Peroxidase

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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