Evaluation of peripheral olfactory pathways in chronic autoimmune thyroiditis

In this study, we aimed to radiologically evaluate the olfactory bulb (OB) volume and olfactory sulcus (OS) depth of adult patients diagnosed with chronic autoimmune thyroiditis.

Sixty-eight patients over 18 years of age with Hashimoto's thyroiditis and 66 healthy controls with normal thyroid function tests were included in the study. OB volume and OS depth measurements were performed using cranial magnetic resonance imaging (MRI) obtained from coronal T2-weighted images. The relationship between thyroid function tests, autoantibodies, and measurements of the OB and OS were evaluated.

The right and left OB volumes were significantly lower in the patients with Hashimoto's thyroiditis than in the control group (p < 0.05). No significant difference was found between the patient and control groups in terms of OS depth (p > 0.05). There were significantly negative correlations among TSH, thyroid antibodies, and the bilateral OB volume measurements. In the Bonferroni post hoc analysis, when people with euthyroid Hashimoto's thyroiditis and the control group were compared, there was no statistically significant difference between bilateral OB volumes and thyroid function tests.

Diminished bilateral OB volumes were found in our patients with chronic autoimmune thyroiditis. Interestingly, the OB volumes were not affected in patients with euthyroid Hashimoto's thyroiditis. When a decrease in OB volume is detected on MRI, it should be kept in mind that odor dysfunction in hypothyroid patients with Hashimoto's thyroiditis may occur and patients should be clinically evaluated.