A positive relationship has been discovered linking heightened ACTH levels in the pituitary to increased hypothyroidism rates, suggesting that stress negatively impacts thyroid functioning. Hypothyroidism is frequently misdiagnosed and treated as depression, yet little is known about this relationship. Nine C57BL/6J subjects were given 0.25% 6-propyl-2-thiouracil per gram for two weeks and twenty-nine were kept on a standard laboratory diet prior to tail suspension testing. The control group was further divided into six-day, single day, and no tail suspension testing. Following the final trail all groups were scored behaviorally in on the open field test. Serum samples were then acquired and T4 levels were calculated. Thyroid status was significantly different between euthyroid (9.87 μg/dL) and hypothyroid (5.50 μg/dL) treatment groups (t (18)=4.57, p< .01). The single day-TST group had significantly greater total activity (t (18) = 2.721, p < .05) and activity >2 volts (t (18) = 2. 886, p < .05) than the six day-TST group. Also, open field behavioral testing showed that single day-TST and hypothyroid groups had less overall movement and more depressed behaviors. These results indicate that low stress and hypothyroidism tend to trigger the symptoms of major depression, but as the stress level increases the symptoms of depression tend to develop into an anxiety disorder. These data have important implications for the treatment of stress-induced affective disorders.
Final Report Form, Research Report