CHANGES OF MORPHOFUNCTIONAL STATE OF THYROID GLAND IN HYPOTHYROID RATS IN CONDITIONS OF INFLUENCE LONG-TERM STRESS

Abstract

Relevance. The chronic stress influences on increasing of frequency of thyroid pathology together with other factors (decreased iodine intake in food, harmful factors of external environment, high technogenic loading, depravation of general ecological state, violation of structure of nutrition). The changes of hypothalamus-hypophysis-thyroid gland axis at stress is not enough agreed because of influence stressful factors with different character and duration.
 Objective is study of influence of chronic emotional painful stress (CS) on the changes of morphofunctional state of thyroid gland (TG) on the background of experimental hypothyroidism (EH).
 Materials and methods. Experiments were performed on 48 white laboratory sex matured male rats. Animals were divided on four groups: the fist – intact animals; the second – animals with EH; the third – animals under influence of CS; the fourth – animals with EH under action of CS. The EH was modeled by everyday addition of mercazolilum (dose 10mg/kg) to drinking water during 15 days. The CS was modeled by 1 hour per day during 30 days. The functional activity of TG was estimated by the concentration of thyroid stimulating hormone (TSH), triiodothyronine (T3), thyroxin (T4) in blood plasma and calculation of thyroid index (TI). The morphological state of TG was studied by light and electron microscopy. The statistical analysis of results was processed using Student’s test with Bonferroni-Holm correction in program Statistica 6.0. The differences were statistical significant at р<0,05. 
 Results. The long-term influence of stress factors caused significant decreasing of level of thyroid hormones in blood plasma in comparison to intact animals. The data of light and electron microscopy of TG of rats under influence of CS confirm biochemical changes and detect signs of decreasing of secretory function. On the background of action of mercazolilum the long-term stress caused to more substantial changes of functional state of TG (significant increasing of level of TSH, decreasing of content of T4 and TI) in comparison to data of animals with EH. The structural features of TG of animals with EH under influence of CS indicate on suppression of function.
 Conclusions. Decreasing of synthesis of hormones by TG in rats at conditions of CS was detected. The long-term action of stress on background of hypothyroidism causes to more substantial depravation of thyroid profile.