Manic and Depressive Bipolar Disorder Events Linked to Thyroid Function

Woman looking shocked
A woman sitting alone and depressed
Mood swings in people with bipolar disorder can happen spontaneously or be triggered by pharmacologic or psychological factors. Researchers investigated whether thyroid function changed when people with the disorder were in a manic or depressive state.

People with bipolar disorder (BD) were found to have significantly different thyroid hormone levels during depressive and manic episodes. These findings, from a cross-sectional study, were published in BMC Endocrine Disorders.

Patients (N=291) with BD were recruited between 2018 and 2019 at the Mental Health Center of West China Hospital. Within 48 hours of hospitalization, blood samples were collected to measure thyroid hormone levels.  Depressive symptoms were assessed using the Montgomery Depression Scale (MADRS) and manic symptoms by the Young Mania Rating Scale (YMRS).

The group was aged mean 27.38±8.01 years, 48.11% were men, and mean age of BD onset was 20.72±6.26 years. Several other factors were noted as well, such as educational level (51.20% had a junior high school education or below) and marital status  (45.36% were unmarried).

At hospital admission, 136 patients were in a manic state, specifically, hypomania (n=16), mania without psychotic symptoms (n=60), and mania with psychotic symptoms (n=60). There were 128 patients in a depressive state, specifically, mild to moderate depression (n=62), major depression without psychotic symptoms (n=43), and major depression with psychotic symptoms (n=23). The remaining patients had mixed symptoms (n=27) and 6 were in remission.

Free triiodothyronine (FT3) levels differed significantly between the patients experiencing manic episodes and depressive episodes.  “The level of FT3, the rate of thyroid hormone increased secretion, and the total abnormality rate of thyroid hormone secretion in the manic group [was] significantly higher than those in the depressive group,” the researchers wrote.

After Bonferroni correction, the abnormality rate of thyroid hormone secretion among patients with mania was significantly higher than depression (69.85% vs 45.31%; P <.005) and mania without psychotic symptoms was higher than depression with psychotic symptoms (70.00% vs 30.43%; P <.005).

Researchers acknowledged the study was limited because thyroid hormone levels were evaluated at a single time point. Additionally, as a cross-sectional study, the researchers said it “cannot be proven whether mood fluctuations in bipolar disorder are related to changes in thyroid function.” 

“These findings indicate that thyroid functions were significantly different between depressive and manic episodes in bipolar disorder patients,” the study authors concluded. “In clinical practice, it is necessary to take into account the differences in thyroid hormone levels in patients with bipolar disorder across different emotional states in choosing [a] drug.”


Zhao S, Zhang X, Zhou Y, et al. Comparison of thyroid function in different emotional states of drug-naïve patients with bipolar disorder. BMC Endocr Disord. 2021;21:210. doi:10.1186/s12902-021-00869-5