Thyroid volume influence

Alcohol consumption is associated with a lower prevalence of goiter and thyroid nodules (Knudsen et ai, 2002). The mechanism behind this association remains unclear. Probably, selenium does not significantly influence thyroid volume in at least borderhne iodine-sufficient populations (Brauer et al, 2006b). Moreover, gender, age and parity can play a role in the pathogenesis of goiter (Knudsen et aly 2002), as discussed later in this article. 

Cardiovascular Effects Thyroid hormones directly and indirectly influence cardiac function, and cardiovascular manifestations are prominent clinical consequences of thyroid disease. In hyperthyroidism, there is tachycardia, increased stroke volume, increased cardiac index, cardiac hypertrophy, decreased peripheral vascular resistance, and increased pulse pressure. In hypothyroidism, there is bradycardia, decreased cardiac index, pericardial effusion, increased peripheral vascular resistance, decreased pulse pressure, and elevation of mean arterial pressure. 

A low thyroid function can influence many of the neuro-humoral systems involved in vascular tone and plasma volume regulation. It has long been known that chronic hypothyroid patients show an increase in peripheral arterial resistance. This is principally due to the lack of direct T3-dependent vasorelaxation and to an increase in arterial wall thickness (Cappola and Ladenson, 2003 Rawat and Satyal, 2004), but enhanced sympathetic activity may also contribute significantly to peripheral vasoconstriction, probably as a powerful compensatory mechanism for the decreased cardiac contractility and intravascular volume which follows TH deprivation. The enhanced sympathetic efflux may eventually overcome a downregulation of post-synaptic vasoconstrictor a-adrenoreceptors, which is described in hypothyroid states, at variance with what is observed in normal physiology, where a positive relationship does exist between TH and the number and activities of noradrenergic receptors (Gomberg-Maitland and Frishman, 1998). 

---