Physical and mental health requires a correct functioning of the thyroid gland, which controls cardiovascular, musculoskeletal, nervous, and immune systems, and affects behavior and cognitive functions. Microgravity, as occurs during space missions, induces morphological and functional changes within the thyroid gland. Here, we review relevant experiments exposing cell cultures (normal and
cancer thyroid cells) to simulated and real microgravity, as well as wild-type and transgenic mice to hypergravity and spaceflight conditions. Well-known mechanisms of damage are presented and new ones, such as changes of gene expression for extracellular matrix and cytoskeleton
proteins, thyrocyte phenotype, sensitivity of thyrocytes to
thyrotropin due to
thyrotropin receptor modification, parafollicular cells and
calcitonin production,
sphingomyelin metabolism, and the expression and movement of
cancer molecules from thyrocytes to
colloids are highlighted. The identification of new mechanisms of thyroid injury is essential for the development of countermeasures, both on the ground and in space, against
thyroid cancer. We also address the question whether normal and
cancer cells show a different sensitivity concerning changes of environmental conditions.