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The following is a summary of “Structural and Functional Alterations of Hippocampal Subfields in Patients With Adult-Onset Primary Hypothyroidism,” published in the July 2024 issue of Endocrinology by Zhang, et al.

Hypothyroidism is often linked to cognitive and emotional dysregulation, yet the specific neuropathological mechanisms underlying these effects are not well understood. For a study, researchers sought to investigate abnormal changes in hippocampal subfield volumes and functional connectivity (FC) in patients with subclinical hypothyroidism (SCH) and overt hypothyroidism (OH) and to examine the correlation between these changes and clinical variables.

They conducted a cross-sectional observational study including 47 patients with newly diagnosed adult-onset primary SCH, 40 patients with newly diagnosed OH, and 53 healthy controls (HCs). They collected data on participants’ demographics, clinical variables, and neuropsychological scale scores. Hippocampal subfield volumes and seed-based FC were compared across the groups, and correlation analyses were performed to explore relationships between thyroid hormone levels and FC values.

Both patients with SCH and OH showed significant cognitive and emotional disturbances compared to HCs. Specifically, the volumes of the right granule cell molecular layer of the dentate gyrus (GC-ML-DG) head, cornu ammonis (CA) 4, and CA3 head were reduced in both SCH and OH groups compared to HCs. Additionally, patients with SCH had more pronounced reductions in the volumes of the right molecular layer head, CA1 body left GC-ML-DG head, and CA4 head compared to HCs. SCH was associated with decreased seed-based FC, while OH showed increased FC relative to HCs. Correlation analyses revealed that thyroid hormone levels were negatively correlated with FC values in hypothyroidism.

The study findings suggested that SCH and OH are associated with cognitive and emotional functioning changes, which correlate with altered hippocampal subfield volumes and functional connectivity. SCH exhibited more significant volume reductions than OH. The results offered new insights into the neuropathological mechanisms of brain impairment in hypothyroidism. They suggested that SCH may present a greater risk for cognitive and emotional issues than OH.

Reference: academic.oup.com/jcem/article-abstract/109/7/1707/7602725