New study associates excess maternal iodine supplementation with congenital hypothyroidism
Congenital hypothyroidism is thyroid hormone deficiency at birth that, if left untreated, can lead to neurocognitive impairments in infants and children. Although the World Health Organization recommends 200-300 µg of iodine daily during pregnancy for normal fetal thyroid hormone production and neurocognitive development, the US Institute of Medicine considers 1,100 µg to be the safe upper limit for daily ingestion. A case series scheduled for publication in The Journal of Pediatrics describes three infants who developed congenital hypothyroidism as a result of excess maternal iodine supplementation.
Kara Connelly, MD, and colleagues from Oregon Health & Science University, Doernbecher Children's Hospital, Boston University School of Medicine, State of Oregon Public Health Laboratory, and Randall Children's Hospital at Legacy Emanuel describe three infants with congenital hypothyroidism whose mothers had taken 12.5 mg of iodine daily, 11 times more than the safe upper limit, while pregnant and/or breastfeeding. Iodine is transferred from the mother to the infant through the placenta or breast milk. The three infants had blood iodine levels 10 times higher than healthy control infants (measured from newborn screening filter paper).
Excess iodine causes the thyroid to temporarily decrease function to protect against hyperthyroidism (Wolff-Chaikoff effect). Adults and older children are able to "escape" from this effect after several days of excess iodine to avoid hypothyroidism. However, the immature thyroid glands of fetuses and newborns have not developed this protective effect and are more susceptible to iodine-induced hypothyroidism. Although infants recover normal thyroid function after acute iodine exposure (e.g., a few days of topical iodine application), continuous excessive iodine exposure to the fetal and neonatal thyroid gland may cause long-term harmful effects on thyroid function.
Sources of iodine include nutritional supplements, prenatal vitamins, and seaweed (kelp). According to Dr. Connelly, "The use of iodine-containing supplements in pregnancy and while breastfeeding is recommended in the United States. However, these cases demonstrate the potential hazard of exceeding the safe upper limit for daily ingestion." Excess iodine ingestion from supplementation is often unrecognized because it is not routine practice to ask mothers of infants with congenital hypothyroidism about nutritional supplements taken during pregnancy. Pregnant or breastfeeding women should discuss the safe dosages of nutritional supplements with their doctors prior to including them in their daily regimen.
More information: Congenital Hypothyroidism Caused by Excess Prenatal Maternal Iodine Ingestion by Kara Connelly, MD, Bruce Boston, MD, Elizabeth Pearce, MD, David Sesser, David Snyder, MD, Lewis Braverman, MD, Sam Pino, Stephen LaFranchi, MD, appears in The Journal of Pediatrics, DOI 10.1016/j.jpeds.2012.05.057
Journal reference: Journal of Pediatrics
Provided by Elsevier
- Researchers urge awareness of dietary iodine intake in postpartum Korean-American women Jul 12, 2011 | not rated yet | 0
- BUSM researchers encourage use of potassium iodide Feb 25, 2009 | not rated yet | 0
- Effects of iodine supplements on maternal thyroid function studied Feb 24, 2010 | not rated yet | 0
- First evidence that a common pollutant may reduce iodine levels in breast milk Oct 13, 2008 | not rated yet | 0
- Harmful effects of hypothyroidism on maternal and fetal health drive new guidelines for managing thyroid disease in preg Jul 25, 2011 | not rated yet | 0
- Motion perception revisited: High Phi effect challenges established motion perception assumptions Apr 23, 2013 | 3 / 5 (2) | 2
- Anything you can do I can do better: Neuromolecular foundations of the superiority illusion (Update) Apr 02, 2013 | 4.5 / 5 (11) | 5
- The visual system as economist: Neural resource allocation in visual adaptation Mar 30, 2013 | 5 / 5 (2) | 9
- Separate lives: Neuronal and organismal lifespans decoupled Mar 27, 2013 | 4.9 / 5 (8) | 0
- Sizing things up: The evolutionary neurobiology of scale invariance Feb 28, 2013 | 4.8 / 5 (10) | 14
Differences of Classical Mechanics when learned with Calc vs algebra?
2 hours ago what are the differences? Every example I find usually has a derivative or integral or some kind of calculus defined concept that seems to make it...
what is the distance traveled
6 hours ago Hi. I have newly started to study mechanical physics. based on study, I conduct a simple experiment. But unfortunately i am unable apply the laws in...
Image of a Convex Lens Cut in Half Horizontally
10 hours ago Hello everyone, A friend of mine came up with this question in class and I really do not have a good answer. Suppose you have a convex lens...
Ray tracing throught optical system of thick lenses
10 hours ago Can you advise me a free software that allow to draw rays passed throught system of thick lenses (preferable in 3D)?
Faraday's law on circular wire
11 hours ago In my examples on Faraday's law in my book, they use a drawing of a magnet approaching a circular wire. The changing magnetic flux then induces an...
Specific Exergy vs Specific Flow Exergy
13 hours ago I'm having some difficulty understanding exactly what the difference between the definitions of these values are. As I understand it, in terms of...
- More from Physics Forums - Classical Physics
More news stories
(HealthDay)—Over the last decade, the number of American children who die each year awaiting an organ donation dropped by more than half, new research reveals. And increasing numbers of children are receiving ...
Pediatrics 3 hours ago | not rated yet | 0
Phthalates: Study links chemicals widely found in plastics, processed food to elevated blood pressure in children, teens
Plastic additives known as phthalates (pronounced THAL-ates) are odorless, colorless and just about everywhere: They turn up in flooring, plastic cups, beach balls, plastic wrap, intravenous tubing and—according to the ...
Pediatrics 15 hours ago | not rated yet | 1 |
A study by Alexandra L. C. Martiniuk, M.Sc, Ph.D., of The George Institute for Global Health, Sydney, Australia, and colleagues suggests less sleep per night is associated with a significant increase in the risk for motor ...
Pediatrics May 20, 2013 | not rated yet | 0
Whole-cell pertussis vaccines were more effective at protecting against pertussis than acellular pertussis vaccines during a large recent outbreak, according to a new Kaiser Permanente study published in Pediatrics.
Pediatrics May 20, 2013 | not rated yet | 0 |
Levels of physical inactivity and obesity are very high in children, with fewer than 50% of primary school-aged boys and fewer than 28% of girls meeting the minimum levels of physical activity required to maintain health. ...
Pediatrics May 17, 2013 | 5 / 5 (1) | 0
Calorie information in fast food restaurants used by 40 percent of 9-18 year olds when making food choices
A new study published online today (Thursday) in the Journal of Public Health has found that of young people who visited fast food or chain restaurants in the U.S. in 2010, girls and youth who were obese were more likely ...
16 minutes ago | not rated yet | 0
(HealthDay)—Migraines and depression can each cause a great deal of suffering, but new research indicates the combination of the two may be linked to something else entirely—a smaller brain.
3 hours ago | 5 / 5 (1) | 0 |
Until now, little was scientifically known about the human potential to cultivate compassion—the emotional state of caring for people who are suffering in a way that motivates altruistic behavior.
3 hours ago | not rated yet | 2 |
Swiss scientists reveal the mechanism responsible for aging hidden deep within mitochondria—and dramatically slow it down in worms by administering antibiotics to the young.
6 hours ago | 4.5 / 5 (2) | 0 |
An independent panel of experts on Wednesday recommended US approval of a new Merck sleeping pill called suvorexant, but expressed concerns over the highest dosage and risks of drowsy daytime driving.
1 hour ago | not rated yet | 0
Researchers from Queen Mary, University of London have led the largest sequencing study of human disease to date, investigating the genetic basis of six autoimmune diseases.
6 hours ago | not rated yet | 0 |