Congenital Hypothyroidism May Reduce Hippocampus Activation in Verbal Memory Processing

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Congenital hypothyroidism may disturb hippocampal associative binding mechanism.
Congenital hypothyroidism may disturb hippocampal associative binding mechanism.

Early thyroid hormone insufficiency may play a role in hippocampal activation patterns for patients with congenital hypothyroidism, according to recently presented data.

Joanne Rovet, PhD, from The Hospital for Sick Children in Toronto, Canada, said in an email interview with Endocrinology Advisor that thyroid hormone is essential for developing the hippocampus and newly associated information.

“Adolescents with congenital hypothyroidism who lacked thyroid hormone in late gestation/very early infancy demonstrate weak verbal recall, reduced hippocampal volumes, and abnormal hippocampal functioning for newly learned visual associations,” Dr Rovet said.

“It is not known if their hippocampus also functions atypically with verbally associated material.”

Dr Rovet and colleagues compared 14 adolescents with congenital hypothyroidism with 14 matched control patients who underwent functional magnetic resonance imaging (fMRI). Patients were given word pairs and single word pairs, and then asked whether they had seen previous words before to engage the right anterior hippocampus.

“Participants silently formed sentences for a series of novel word pairs and in the scanner, received 2 retrieval tasks. These showed words in original or rearranged pairs or with 1 or 2 new words,” Dr Rovet said.

“In [p]airs, they judged if words were paired before and in items, if words were seen before regardless of pairing.”

The researchers found that, while patients with congenital hypothyroidism and control patients were both accurate, there was increased hippocampal activation during word pair associations, with the control group showing significantly increased right anterior hippocampus activity.

Patients with congenital hypothyroidism also had less activation of the left middle hippocampus during word pair associations.

“Specifically, controls activated right anterior hippocampus for word pairs and strongly deactivated it for individual items, whereas congenital hypothyroidism [patients] showed little differentiation between pairs or items,” Dr Rovet said.

The researchers noted that reduced hippocampus activity during word pair associations may show decreased hippocampal integrity for verbal memory processing.

“These findings suggest [patients with congenital hypothyroidism] have less specialized and adequate hippocampal function and may signify their hippocampal associative binding mechanism has been disturbed by their early thyroid hormone insufficiency,” Dr Rovet said.

Reference

  1. Rovet J, McClelland V, Wheeler S, McAndrews M. Oral Abstract 8. Atypical Hippocampal Functioning During Verbal Memory Recall In Youth With Congenital Hypothyroidism. Presented at: 15th International Thyroid Congress and 85th Annual Meeting of the American Thyroid Association (ITC/ATA); October 18-23, 2015; Lake Buena Vista, Florida.
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