Effects of secondhand smoke on thyroid function.

Growing evidence suggests that the effects of second hand smoke (SHS) exposure contribute to disruptions in thyroid function. Toxic elements contained in cigarette smoke, such as thiocyanate, may be partially responsible for impaired thyroid hormonogenesis. SHS-induced inflammatory stress, namely interleukin 1beta (IL-1beta), impairs thyroid hormonogenesis and iodine uptake; initiates interleukin 6 (IL-6) production from thyroid epithelial cells and stimulates the expression of molecules that exacerbate thyroid autoimmunity. The link between SHS exposure and thyroid autoimmune disease is not well documented and thus, remains to be fully understood. Elevated inflammatory stress and thyroid hormone secretion in response to SHS exposure initiates catabolic processes that alter body composition via lean body mass breakdown; translating to an elevation in resting energy expenditure of approximately 10%. The combination of certain biological factors, such as sex and/or existing thyroid disease may stimulate differential SHS-induced effects on thyroid function. Nevertheless, exposure to SHS disturbs vital human processes via thyroid disruption.