ABSTRACT
BACKGROUND: Previous studies have suggested an association between subclinical hypothyroidism and coronary artery disease that could be related to changes in serum lipids or endothelial dysfunction. METHODS: Thirty-two female subclinical hypothyroidism patients were randomly assigned to 12 months of L-thyroxine replacement or no treatment. Endothelial function was measured by the flow-mediated vasodilatation of the brachial artery, as well as mean carotid artery intima-media thickness, and lipid profiles were studied at baseline and after 12 months of follow-up. RESULTS: The mean ( ± SD) serum thyroid-stimulating hormone levels in the L-thyroxine replacement and control groups were 6.09±1.32 and 6.27 ± 1.39 μUI/ml, respectively. No relationship between carotid artery intima-media thickness or brachial flow-mediated vasodilatation and free T4 and serum thyroid-stimulating hormone was found. The median L-T4 dose was 44.23 ± 18.13 μg/day. After 12 months, there was a significant decrease in the flow-mediated vasodilatation in the subclinical hypothyroidism control group (before: 17.33 ± 7.88 to after: 13.1 ±4.75 percent, p =0.03), but there were no significant differences in flow-mediated vasodilatation in the L-thyroxine treated group (before: 16.81 ± 7.0 to after: 18.52 ± 7.44 percent, p = 0.39). We did not find any significant change in mean carotid intimamedia thickness after 12 months of L-thyroxine treatment. CONCLUSION: Replacement therapy prevents a decline in flow-mediated vasodilatation with continuation of the subclinical hypothyroidism state. Large prospective multicenter placebo-controlled trials are necessaryto investigate endothelial physiology further in subclinical hypothyroidism patients and to define the role of L-thyroxine therapy in improving endothelial function in these patients.
Subject(s)
Adult , Female , Humans , Male , Middle Aged , Carotid Intima-Media Thickness , Hormone Replacement Therapy , Hypothyroidism/drug therapy , Thyrotropin/blood , Thyroxine/therapeutic use , Endothelium, Vascular/drug effects , Endothelium, Vascular/physiology , Follow-Up Studies , Hypothyroidism/blood , Hypothyroidism/physiopathology , Prospective Studies , Regional Blood Flow/drug effects , Vasodilation/physiologyABSTRACT
O papel do endotélio em várias doenças vem sendo o foco da investigação científica e recentemente estão disponíveis métodos de avaliação da função endotelial de menor custo e menos invasivos. O endotélio modula o tônus vascular, participa dos processos inflamatórios, da ativação de plaquetas e da trombose. Consequentemente, a disfunção endotelial tem sido considerada evento importante na patogênese da aterosclerose. O hipotireoidismo está associado a maior risco cardiovascular, e a avaliação da função endotelial vem sendo reconhecida como ferramenta promissora na detecção de alterações cardiovasculares pré-clínicas associadas à disfunção tireoidiana. Alguns estudos recentes demonstraram relação entre o status tireoidiano e a função endotelial. Entretanto, estudos multicêntricos e controlados por placebo são necessários para abordar essa questão e o efeito da reposição da levotiroxina na função endotelial. Esse artigo propõe-se a discutir as perspectivas da relação entre endotélio e função tireoidiana.
The role of the endothelium in human disease has become the focus of scientific investigation and recently noninvasive and less expensive measures of endothelial function have become available. The endothelium modulates the vascular tonus and participates in inflammatory processes, platelet aggregation and thrombosis. Consequently, endothelial dysfunction has been implicated as an important event in the pathogenesis of atherosclerosis. Hypothyroidism is associated with an increased cardiovascular risk, and the assessment of endothelial function holds a great deal of promise as an assessment tool for the detection of preclinical cardiovascular alterations associated with thyroid dysfunction. Some recent studies have demonstrated a relationship between thyroid status and endothelial function, but large multicenter, placebo-controlled prospective trials are necessary to address this issue and the effect of levothyroxine replacement treatment in endothelial function. The objective of this work is to discuss the perspective picture in endothelium and thyroid function relationship.