Stress - Chronic physiologic stress results in decreased D1 activity (11,12,13-17,234) and an increase in D3 activity (1,195,196), decreasing thyroid activity by converting T4 into reverse T3 instead of T3 (1,195,196,216,234). Conversely, D2 is stimulated, which results in increased T4 to T3 conversion in the pituitary and reduced production of TSH (11,16,18-22,234). The increased cortisol levels seen with stress also contribute to physiologic disconnect between the TSH and peripheral tissue T3 levels (16,18-20). This stress induced reduced tissue T3 level and increased reverse T3 results in tissue hypothyroidism and potential weight gain, fatigue, and depression (12,13,194,217-219).
***This vicious cycle of weight gain, fatigue, and depression that is associated with stress can be prevented with supplementation with timed-released T3 (25,26,52,121-124,199,201-215,220,221) but not T4 (52,197-199,201,222,223).*****