thyroxine – ABC CARDIOL

IJCS

Editorial

Hyperthyroidism and Cardiac Contractility

Dhiãnah Santini de Oliveira Chachamovitz

Much information is lacking on hyperthyroidism and cardiac function, especially in isolated muscles. Certainly, the time the heart muscle is exposed to elevated thyroid hormones (TH) influences the magnitude of their effects. The primary changes seem to be related to increases in the heart mass/body mass ratio and in relaxation kinetics.

These cardiac changes may also be related not only to the time of exposure to excess thyroid hormones, but to the level or intensity of hyperthyroidism, as well as the underlying cardiac condition, which may reflect exercise conditioning and overload. In this sense, the cellular mechanisms of muscle adaptation, energy and oxygen consumption, certainly make differences. As well as muscle strength and sarcoplasmic/endoplasmic reticulum calcium (SRCa) activity, they may also have different individual adaptive characteristics.

[…]

Read Full Article

ABC

Artigo Original

Spironolactone effects on myocardium changes induced by thyroid hormone in rats

Maria Luiza Mendonça Pereira Fernandes et al. Eloísa Amália Vieira Ferro Marcelo Emilio Beletti Elmiro Santos Resende

BACKGROUND: To study the possible role of aldosterone on thyroid hormone-induced myocardium hypertrophy, using spironolactone. OBJECTIVE: To evaluate morphological changes in the myocardium induced by thyroid hormone and the possible effects of spironolactone use on these alterations. METHODS: Forty Wistar rats were studied. The animals were allocated to four groups and were given: the vehicle used for dilution of the thyroid hormone (C); sodium levothyroxin at 50 µg/rat/day (H); spironolactone, 0.3 mg/kg/day (S); or thyroid hormone plus spironolactone (HS), at the same doses mentioned above, for 28 consecutive days. All the animals were weighed, had blood drawn for hormonal measurements and underwent ECG at the start and the end of the experiment. At the end of experiment all animals were euthanized, the weight of the left ventricle (LV) was determined and LV slices were obtained for morphological analysis. RESULTS: There was an increase in T3 levels, decrease of body weight and higher heart rate in the animals from group H. The LV weight was significantly higher in the H e HS groups. The histometric analyses that measured the diameter of the myocytes showed higher values in group H and a progressive decrease in groups HS, S and C, with a significant difference among all the groups. The addition of spironolactone decreased the transversal myocyte hypertrophy by 14.6%. CONCLUSION: Rats treated with thyroid hormone present cardiac hypertrophy with increased LV weight and greater myocyte diameter. Spironolactone, when associated with thyroid hormone, can partially prevent this hypertrophy through mechanisms that are yet to be determined.

Read Full Article

Hyperthyroidism and Cardiac Contractility

Spironolactone effects on myocardium changes induced by thyroid hormone in rats

Electronic Document Format (Vancouver)

Electronic Document Format (ABNT)

Electronic Document Format (APA)

Electronic Document Format (ISO)

Electronic Document Format (Vancouver)

Electronic Document Format (ABNT)

Electronic Document Format (APA)

Electronic Document Format (ISO)