We have been studying specifics of interactions between immune system and thyroid status among inhabitants of radioactive contaminated areas who suffered further emotional stress. The research involved 70 people from relatively environmentally friendly areas (control group) and 100 people from the radiation zone IV. All examined are National University of Cherkasy students aged 18 to 24 years. The main factor that led to the formation of emotional stress was winter examination session. It was determined that 48% of examined taken from the areas of enhanced radiation monitoring showed the signs of hyperthyroidism. In this case, people with high content of triiodothyronine (Т3) in peripheral blood showed some definite tension in their thyroid system, which was characterized by increasing concentration of thyrotrophic hormone (TSH, 3.67±0.25 μIU/mL compared with control group – 2.31±0.21 μIU/mL). Under conditions of additional emotional stress in patients with symptoms of hyperthyroidism a significant reduction of triiodothyronine level was observed (from 2.59±0.07 to 1.71±0.07 nmol/l) along with the absence of changes in thyroxine level and tendency to reduction of TSH. This effect was also accompanied by a decrease in correlation index between T3 level and some definite indicators of cellular immunity. The revealed features may indicate a depletion of adaptive capacity of thyroid system caused by the prolonged effects of low doses of ionizing radiation.