Hypothyroxinemia Induced by Mild
Iodine Deficiency Deregulates Thyroid
Proteins during Gestation and Lactation
in Dams
By Wei Wei, Yi Wang, Jing Dong, Yaun Wang, Hui Min, Binbin
Song, Zhongyan Shan, Weiping Teng, Qi Xi, and Jie Chen
Melissa Zargham
Purpose
• The object of the study was to explore the effect of mild iodine deficiencyinduced maternal hypothyroxinemia during pregnancy and lactation on
thyroidal proteins.
• Importance: Maternal iodine deficiency during pregnancy and lactation
results in decreased IQ in children.
Introduction
• Iodine = essential trace element for the thyroid
•
Produces triiodothyronine (T3) and thyroxine (T4)
• Iodine deficiency (ID) can lead to
•
•
Hypothyrodism
Hypothyroxinemia
• Mild ID is recognized as the most common reason causing
hypothyroxinemia
Introduction
• Thyroid and Thyroid function:
•
•
Thyroid transcription factor 1 (TTF1)
Paired box gene 8 (PAX8)
• Thyroid hormone
•
•
Type 1 iodothyronine deiodinase (DIO1)
Type 2 iodothyronine deiodinase (DIO2)
Background
•
Thyroid Hormone Synthesis
•
•
•
•
•
Iodide (I-) actively taken up into the thyroid cells
Iodide is oxidized to iodine and bound to the
tyrosyl residues of thyroglobulin forming
thyroglobulin-3-monoiodotyrosine (Thg-MIT)
MIT is iodinated in the 5th position forming ThgDIT
Two DITs couple to form Thg-T4. DIT also couples
with MIT to form T3
Thg-T4 and Thg-T3 are hydrolyzed by lysosomal
proteases and T4 and T3 are released into blood
Hypothesis
• Mild ID diet may induce mild ID by impacting the expressions of thyroidal
TTF1, PAX8, and NIS. In gestational and lactational dams, mild ID may
induce hypothyroxinemia and disturb thyroidal DIO1 and DIO2 expressions.
Methods
•
•
•
•
Female Wistar rats
Three groups:
•
•
•
Control group ( iodine intake of 7.0 μg/day)
Mild ID group (iodine intake of 3.0 μg/day)
Severe ID group (iodine intake of 1.5 μg/day)
Blood was obtained and tested via a supersensitive chemiluminescence
immunoassay
Mated with normal male rats
Methods
•
Measurement of Thyroid Iodine Content:
•
•
•
Thyroid glands were collected from 5 dams on
gestational day (GD)19 and postpartum day
(PN) 21
Measured by ammonium persulfate-arsenic
cerium catalytic spectrophotometry
Western Blotting
•
•
•
Rats were euthanized
Thyroid gland tissue was collected
Chemiluminescence
Results
•
•
Thyroid Iodine Content: Thyroid gland weight
significantly increased in mild and severe ID
Western Blotting:
Western Blotting Results
Results
DIO1
DIO2
Discussion/Conclusion
•
•
•
•
Major findings:
•
Increased thyroid weights, decreased thyroid iodine contents and up-regulation of thyroidal
TTF1, PAX8, NIS, DIO1 and DIO2
Hypothyroidism induced by severed ID not common but hypothyroxinemia still
prevalent
Maternal hypothyroxinemia may lead to irreversible CNS damage in humans.
Results showed that, in the gestational and lactational dams, the maternal mild ID
diet could cause mild ID by impacting thyroidal TTF1, PAX8, and NIS. Also,
hypothyroxinemia induced by mild ID increased the levels of DIO1 and DIO2.
Resources
• Western Blotting Image http://www.piercenet.com/guide/fast-westernblotting-product-selection-guide
• Wei, W., Wang, Y., Dong, J., Wang, Y., Min, H., Song, B., . . . Chen, J. (2013).
Hypothyroxinemia induced by mild iodine deficiency deregulats thyroid
proteins during gestation and lactation in dams. International Journal of
Environmental Research and Public Health, 10(8), 3233-45. Retrieved from
http://search.proquest.com/docview/1468936671?accountid=13645
• Gropper, S & Smith, J. Essential Trace and Ultratrace Minerals. Advanced
Nutrition and Human Metabolism (6th ed.). (pp.531-533). Belmont:
Wadsworth Cengage Learning.