Thyroid hormone in health and disease

Abstract

Thyroid disease is common, affecting around 2% of women and 0·2% of men in the UK. Our understanding of the effects of thyroid hormones under physiological circumstances, as well as in pathological conditions, has increased dramatically during the last two centuries and it has become clear that overt thyroid dysfunction is associated with significant morbidity and mortality. Both hypoand hyperthyroidism and their treatments have been linked with increased risk from cardiovascular disease and the adverse effects of thyrotoxicosis in terms of osteoporosis risk are well established. Although the evidence suggests that successful treatment of overt thyroid dysfunction significantly improves overall survival, the issue of treating mild or subclinical hyper-and hypothyroidism remains controversial. Furthermore, the now wellestablished effects of thyroid hormones on neurodevelopment have sparked a whole new debate regarding the need to screen pregnant women for thyroid function abnormalities. This review describes the current evidence of the effects of thyroid hormone on the cardiovascular, skeletal and neurological systems, as well as the influence of thyroid diseases and their treatments on the development of malignancy. Furthermore we will describe some recent developments in our understanding of the relationship between thyroid status and health.

Serum PCBs, p,p′-DDE and HCB predict thyroid hormone levels in men

“…We also found that p,p′-DDE was associated with increased free T 4 and total T 3 , and inversely associated with TSH. Studies on adverse health effects associated with small changes in thyroid hormones in humans are limited (Boelaert and Franklyn 2005;Surks et al 2004), and the changes found in the present study may not be clinically important at the individual level. However, due to the pervasiveness of exposure to these compounds there may be consequences related to small changes in thyroid hormone levels among entire subsets of the population.…”

“…Although the consequences of sub-clinical changes in thyroid hormones are currently not well understood (Boelaert and Franklyn 2005;Surks et al 2004), factors associated with any alteration in thyroid hormone levels are of concern. Several environmental agents, most notably organochlorine pesticides and polychlorinated biphenyls (PCBs), have been found to influence thyroid hormone activity and metabolism (Zoeller 2005;Qatani et al 2005;Bogazzi et al 2003).…”

Free Triiodothyronine Concentrations are Inversely Associated with Elevated Carotid Intima-Media Thickness in Middle-Aged and Elderly Chinese Population

“…The impact of thyroid function on cardiovascular morbidity and mortality has received much atten-tion over the past years 1,2) . Overt hypothyroidism is associated with abnormal lipid metabolism and impaired endothelial function as well as increased risk of atherosclerosis and ischemic heart disease 3,4) .…”

Thyroid hormones and cognitive functioning in healthy, euthyroid women: A correlational study

“…In healthy individuals, neuroendocrine feedback mechanisms ensure that T3 and T4 are maintained within normal limits. Levels of THs within the normal range are crucial for the maintenance of various physiological and cognitive functions such as attention, memory, and mood (for review see Boelaert and Franklyn, 2005;Smith et al, 2002).…”