Correlation between Intrinsic Brain Activity and Thyroid-Stimulating Hormone Level in Unmedicated Bipolar II...

Although abnormalities of amplitude of low-frequency fluctuations (ALFF) and hormone levels of hypothalamus-pituitary-thyroid axis have been reported in patients with bipolar disorder (BD), the association between abnormal ALFF and serum thyroid hormone levels remains unknown.

A total of 90 patients with unmedicated BD II depression and 100 healthy controls (HCs) underwent resting-state functional magnetic resonance imaging, and then routine band (0.01-0.1 Hz), slow-5 band (0.01-0.027 Hz), and slow-4 band (0.027-0.073 Hz) ALFF analysis were performed. Additionally, serum thyroid hormone levels including free tri-iodothyronine (FT3), total tri-iodothyronine (TT3), free thyroxin (FT4), total thyroxin (TT4), and thyroid-stimulating hormone (TSH) were detected. The correlation between abnormal serum thyroid hormone levels and ALFF values in patients with BD II depression was calculated.

Compared with the HCs, patients with BD II depression showed decreased ALFF in bilateral precuneus (PCu)/posterior cingulate cortex (PCC) in routine and slow-4 frequency bands, decreased ALFF in the right PCu, and increased ALFF in the right middle occipital gyrus (MOG) in the slow-5 frequency band. Additionally, patients with BD II depression showed lower TSH level than HCs, and TSH level was positively correlated with ALFF values in the bilateral PCu/PCC in the routine frequency band.

These findings suggest that patients with BD II depression display intrinsic activity abnormalities, mainly in the PCu/PCC and MOG, which are associated with specific frequency bands. Moreover, altered intrinsic activity in the PCu/PCC may be related to TSH levels in bipolar II depression.