Hypothyroidism is a common disease and it is associated with prolonged stable deficiency of thyroid hormones in the body or with the deficiency of their biological effect on the tissue level. Deficiency of thyroid hormones in the body leads to disruption of water-electrolyte, protein, lipid, carbohydrate metabolism, causing morphofunctional and biochemical changes in various organs and systems, particularly in the organs of the musculoskeletal system. Study of morphofunctional changes in organs of musculoskeletal system in the deficiency of thyroid hormones remained unnoticed by the researchers, while these data could serve as the theoretical basis for understanding of the pathogenesis of diseases of the musculoskeletal system in hypothyroidism and development of the adequate methods of their diagnosis, treatment and prevention. Therefore, the objective of the study was to determine morphofunctional peculiarities of the ultrastructural organization of the components of temporomandibular joint and masticatory muscles during the 14th and 21st days after the development of induced hypothyroidism. The study was performed on 40 white outbred male rats. To model hypothyroidism the medicine “Mercazolilum” (“Zdorovya”, Ukraine) was used, it was administered in drinking water at corresponding doses – 7.5 mg per 100 g of animal’s body weight (after the 14th day – 3.5 mg per 100 g of animal’s body weight). Euthanasia – was performed by introduction of sodium thiopental. Animal management, their nutrition and manipulations with them were performed in compliance with ethical and legal standards and requirements. Collection of material (temporomandibular joint, proper chewing and lateral pterygoid muscles) was performed during the 14th and 21st days of the modeled hypothyroidism followed by electronic-microscopic study. During the 14th day there are edematous changes in the wall of hemocapillaries, connective tissue elements of the capsule and articular surface of the temporomandibular joint, and also in striated muscular fibers of masticatory muscles and their endo- and perimysium. During the 21st day a significant strengthening of edematous changes in hemocapillaries, components of the temporomandibular joint and masticatory muscles occur, which in turn leads to hypoxia and dysfunction of these organs. Such morphofunctional transformations in the studied structures indicate the need to study the changes in the dynamics to find some possibilities of prevention and treatment.
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