Posted by Phillipa on November 4, 2011, at 0:03:01
Maybe part of the missing link? Moms with hypothyroidism have offspring with Hippocampal Differences and memory? Phillipa
Medscape Medical News from the:
American Thyroid Association (ATA) 81st Annual MeetingThis coverage is not sanctioned by, nor a part of, the American Thyroid Association.
From Medscape Medical News
Hippocampal Differences Related To Maternal Hypothyroidism
Nancy A. MelvilleAuthors and Disclosures
November 2, 2011 (Indian Wells, California) Children whose mothers experienced hypothyroidism during pregnancy show significantly abnormal hippocampal functioning during the recall of autobiographic memories, according to research presented here at the American Thyroid Association (ATA) 81st Annual Meeting.
Thyroid hormone is known to play a critical role in the development of the hippocampal region of the brain. Extensive basic research has demonstrated detrimental effects on brain development in the offspring of hypothyroid rodents, explained coauthor Joanne Rovet, PhD, a senior scientist in psychology at the Hospital for Sick Children in Toronto, Ontario, Canada.
"The offspring of hypothyroid rodents show effects on brain development such as small neurons, reduced glucose uptake, and an abnormal migration of cells in the hippocampus during development," Dr. Rovet said.
It has been shown that the hippocampus becomes activated to a greater degree in response to episodic autobiographic memory, so Dr. Rovet and her colleagues sought to investigate how maternal hypothyroidism affects the autobiographic memory of their children.
The study involved 34 children 9 to 11 years of age. Of these, 15 had mothers who had overt hypothyroidism during pregnancy. The remaining 19 served as control subjects. All participants received 1-hour magnetic resonance imaging (MRI) sessions that included functional MRI testing.
During the MRI, the children were given an autobiographic memory retrieval task with yes/no questions about memories of specific events and a control condition with yes/no questions to assess general semantic memory facts.
The functional MRI results showed significant differences in autobiographic memory between those whose mothers had hypothyroidism during pregnancy and those in the control group.
"After controlling for total hippocampal volumes and accuracy, maternal TSH [thyroid-stimulating hormone] levels during the first trimester of pregnancy significantly predicted hippocampal activations during autobiographic memory," compared with fact retrieval, the authors report.
Among children with mothers who had higher first-trimester TSH values, there was significantly greater left hippocampus activity (P = .002) and greater right hippocampus activity (P = .42).
"Behaviorally, we found that the offspring of hypothyroid women provided less detail in their original autobiographic memories," Dr. Rovet told Medscape Medical News. "When they recalled their own past, it was with less detail."
"On recalling events that had been staged for the study, they were significantly less accurate than the nonmaternal hypothyroid controls, and the degree of accuracy on the staged memory correlated with their hippocampal volume."
Furthermore, the degree of hippocampal activity, representing greater difficulty recalling memories, corresponded with the degree of maternal hypothyroidism, Dr. Rovet added.
"When we correlated the amount of activation in the hypothyroid group, we found that those whose mothers had more severe hypothyroidism during pregnancy had to activate their hippocampus more to remember their own past experiences as they came into adolescence."
The results underscore the need to look at the potentially broader developmental implications of maternal hypothyroidism in pregnancy, she added.
"We need to do activity analyses to see how the whole brain is functioning in these children," Dr. Rovet emphasized. She noted that her research team currently has a grant under review to look at the implications for everyday memory activity such as social problem solving, future planning, and memory.
Alex Stagnaro-Green, MD, senior associate dean for education at the George Washington University School of Medicine in DC, agrees that the findings should be followed up with more rigorous research.
"These are very intriguing findings. [It] has definitely been suggested, in animal models, that there are other defects in the offspring of maternal hypothyroidism; this now puts things into the human arena.
"The big question is what the clinical impact is," Dr. Stagnaro-Green noted.
Amid mounting research demonstrating the adverse effects of thyroid disease during pregnancy for the mother and child alike, the ATA recently released clinical guidelines for the treatment of women with hypothyroidism during pregnancy.
Some of the key recommendations are to treat women with overt or subclinical hypothyroidism who are positive for thyroid peroxidase antibodies with oral levothyroxine, to monitor women with subclinical disease for progression to overt hypothyroidism, and to avoid other thyroid preparations such as triiodothyronine.
Although there is debate about whether the guidelines should recommend universal screening, Dr. Stagnaro-Green said he doesn't think these findings are strong enough yet to bolster the universal screening argument.
"This study shows a difference on MRI, but whether that has any practical significance, we don't know. Before we recommend universal screening for more than 4 billion women a year, we want to make sure the data are more solid," he cautioned.
The authors and Dr. Stagnaro-Green have disclosed no relevant financial relationships.
American Thyroid Association (ATA) 81st Annual Meeting: Abstract 1. Presented October 27, 2011.
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URL: http://www.dr-bob.org/babble/20111027/msgs/1001614.html