The Effects of Hypothyroidism on the Mechanical Properties and Histomorphological Structure of the Thoracic Aorta

Abstract

This experimental study investigates the effects of hypothyroidism on the descending thoracic aorta. Hypothyroidism was induced in 20 male Wistar rats by administering 0.05% of 6-n propyl 2-thiouracil (PTU) in their drinking water for 8 weeks. Euthyroid rats were used as controls. Animals were sacrificed and longitudinal strips of the descending aorta were subjected to various preselected levels of stress in a uniaxial tensile-testing device. Analysis of stress-strain, elastic modulus-strain curves disclosed significant differences between groups, indicative of stiffer aortas in hypothyroid animals at the upper physiologic and higher levels of pressure. Remodeling of the aortic wall of hypothyroid animals revealed significant histological changes. The thoracic aorta of hypothyroid rats compared with that of euthyroid ones became stiffer at high strains, including the upper physiologic range, loosing part of its distensibility. Hypothyroidism was also associated with diameter enlargement and substantial lengthening of the aorta.

Thyroid hormone dysfunctions affect the structure of rat thoracic aorta: a histological and morphometric study

“…The previous authors added that at physiologic pressure, the stiffness is determined by both elastin and collagen content [27]. The impairment of the elastic properties of the aorta and the marked increase in its collagen content are associated mostly with increased stiffness of the aorta and decrease of its distensibility [20,30]. The impairment of aortic elastic properties in hyperthyroidism may be due to the direct effect of the thyroid hormones on the aorta and due to the modulate effects of thyroid hormones on the vascular renin-angiotensin system [1].…”

“…Alterations in thyroid hormone levels have a profound impact on the cardiovascular system [13]. Cardiovascular dysfunction has been associated with both hyperthyroidism and hypothyroidism [13,20]. In hypothyroidism, the cardiovascular dysfunctions are decreased cardiac contractility, cardiac output, heart rate, and left ventricular compliance with increased total peripheral vascular resistance [21].…”

“…In addition, the data on the histological composition in human aortas of hypothyroid patients are scarce [20].…”

Impaired aortic distensibility in hypothyroid patients with negative coronary angiograms: Simultaneous evaluation with 128-slice multiple row detector computed tomography

“…4 Aortic distensibility, which relates to the degree of contraction and expansion of the aorta, is a property of the vascular wall itself: it is affected by several factors and is related to hypothyroidism. 3,5 Simultaneous evaluation of the coronary angiogram and aortic elasticity is important to estimate the risk of developing coronary artery disease, 4 with aortic distensibility emerging as a useful predictor of coronary artery disease risk. 6 The thoracic aorta is easily accessible by 128-slice multiple row detector computed tomography (MDCT) during coronary angiograms, and MDCT has been shown to provide an objective calculation of aortic distensibility.…”

O efeito do hipotiroidismo experimental sobre os componentes da matriz extracelular de aortas torácicas de ratos.

“…No tocante às variações de peso em ratos submetidos ao hipotiroidismo, muitas são as controvérsias. O grau e o tempo de hipotiroidismo podem alterar a massa corpórea dos animais, mas em geral, a maioria dos estudos que se utilizam deste modelo apresentam perda de peso dos animais submetidos a este estado (CARNEIRO-RAMOS et al, 2007;MOULAKAKIS et al, 2008;MOULAKAKIS et al, 2010).…”