Study Of The Relationship Between Thyroid Function And Depressive Disorder

Thyroid dysfunction is closely related to depressive disorder, both hyperthyroidism and hypothyroidism can lead to depressive disorder; hypothyroidism and depression have similar clinical manifestations, both of them can cause cognitive defects. The mechanism under which thyroid disfunction leads to depressive disorder is still unclear, the following study was performed in order to explore the relationship between thyroid function and depressive disorder:1. The open field test and sucrose preference test were performed to evaluate the behavioural changes of the hypothyroid rats, F-FDG micro PET imaging was conducted to evaluate the changes in glucose metabolism of the brain, and the relationship between the behavioural manifestations and the brain metabolism were analyzed. Body weight, sucrose preference, feces boli and rearing in the open field test decreased significantly in the hypothyroid rats compared to the control rats; the glucose metabolism decreased bilaterally and significantly in caudate/putamen, cortex cingulate, nucleus accumbens, cortex frontal association and cortex motor in the hypothyriod rats; the metabolic changes in caudate/putamen and nucleus accumbens correlated significantly with changes in sucrose preference.2. Depression occured more frequently in patients with subclinical hypothyroidism (23.5%) after131I treatment than in euthyroid patients (7.3%). L-thyroxine treatment was performed in some patients with TSH level higher than10mlU/L in the subclinical hypothyroidism group, significant decrease in HAMD score was observed which demonstated the beneficial effects of substitutive treatment.3. Scale evaluation and clinical data analysis were conducted in patients with Graves’ diseae in an attempt to explore the risk factors of depression and anxiety in hyperthyroidism, usefulness of SF-36was evaluated in GD patients. Results showed that depression and anxiety were more prevalent in patients with Graves’disease, FT3, FT4, TRAb and eye symptoms were risk factors for depression, FT3, heart rate and thyroid swelling were risk factors for anxiety, SF-36was a suitable tool in the evaluation of life quality in GD patients.4. Regional brain blood flow changes in patients with depression and hypothyroidsm were compared using SPECT, cognitive function was evaluated with Go/No go test. Relative rCBF decreased significantly in bilateral caudate and right cingulate for depressive patients and in bilateral prefrontal cortex, anterior central gyrus, posterior central gyrus, hippocampus, superior parietal lobule and cingulate for hypothyroid patients. Both depressive and hypothyroid patients had significant higher HAMD scores than contol patients, HAMD score in the depressive group correlated negatively with rCBF in bileteral cingulate and caudate, while HAMD score in the hypothyroid group correlated negatively with rCBF in bilateral cingulate; cognitive defects were observed in both depressive and hypothyroid groups, Go/No go score correlated positively with relative rCBF in prefrontal cortex in the depressive group, while correlated positively with prefrontal cortex and hippocampus in the hypothyroid group.In conclusion, hypothyroidism can lead to decrease in regional brain glucose metabolism in rats, abnormal brain metabolism relates closely to depressive symptoms, thyroid hormone deficiency can influnce the function of emotional circuit which subsequently causes depressive disorder; both depression and hypothyroidism can lead to abnormality in regional brain blood flow, and some of the abnormal regions overlap in the two diseases which means similar neural mechanism underlies the mood and cognitive disorders in depressive and hypothyroid patients; subclinical hypothyroidism increases the incidence of depression, L-thyroxine substitution can improve the depressive symptoms in patients with subclinical hypothyroidism; FT3, FT4, TRAb and eye symptoms are risk factors of depression in Graves’ disease, FT3, heart rate and thyroid swelling are risk factors of anxiety in Graves’disease, SF-36can reflect the life quality of patients with Graves" disease.