The changes of thyroid follicular endocrinocytes and elements of microcirculatory bed were studied in 102 albino outbred malerats subjected to dynamic and static physical loads using the complex of methods of light microscopic morphometry and statistical data processing with the application of correlation analysis. The results of the study demonstrated that the general peculiarity of the load effect was its phase character with a minimum of thyroid activity at day 10 of experiment. Changes during dynamic load were found to appear later; with the peaks of indexes of thyrocyte hormone production activity at days 5 and 40, these were accompanied by the congestion of veins and arteries. During the static load, changes appeared earlier; peaks of activity were detected at days 3 and 20, and were accompanied by plethora of veins and emptiness of arterial lumen. The activity of thyroid follicular endocrinocytes was reduced at days 5 and 30; this was accompanied by their desquamation, plasmorrhagia and expansion of interlobular spaces.