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Yonsei Med J. 2010 Jul;51(4):492-8. doi: 10.3349/ymj.2010.51.4.492.

Endothelial function is not changed during short-term withdrawal of thyroxine in patients with differentiated thyroid cancer and low cardiovascular risk.

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1
Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.

Abstract

PURPOSE:

The incidence of differentiated thyroid cancer is increasing in young adults and females in Korea. Some of them experience short-term hypothyroidism in preparation for radioiodine (RAI) therapy, which can have a deleterious effect on the cardiovascular system. However, it is not clear if short-term hypothyroidism induces endothelial dysfunction in patients with low cardiovascular risk. Therefore, the aim of this study was to investigate whether short-term hypothyroidism is associated with endothelial dysfunction in patients with low cardiovascular risk.

MATERIALS AND METHODS:

To evaluate the effect of short-term hypothyroidism on endothelial function in this group, we recruited fifteen female patients with low cardiovascular risk. We analyzed clinical, biochemical, and cardiovascular parameters at four time points: the last day on levothyroxine (LT4) at their usual thyroid-stimulating hormone (TSH)-suppressive doses (P1), 7 days (P2) and 4 weeks (P3) after withdrawal of LT4, and 8 weeks (P4) after replacement of the previous dose of LT4. A high resolution ultrasound was used to measure brachial artery diameter at rest, after reactive hyperemia, and after sublingual nitroglycerin.

RESULTS:

During short-term hypothyroidism (P3), serum concentrations of total cholesterol and low-density lipoprotein (LDL)-cholesterol were increased (p < 0.001 for each period). In spite of having worsened lipid states, serum high sensitivity C-reactive protein or flow-mediated vasodilatation, which is one of the surrogate markers of the endothelial function, did not change during short-term hypothyroidism.

CONCLUSION:

Short-term hypothyroidism induced worsening of metabolic parameters, but not enough to induce the endothelial dysfunction in patients with low cardiovascular risk.

PMID:
20499412
PMCID:
PMC2880259
DOI:
10.3349/ymj.2010.51.4.492
[Indexed for MEDLINE]
Free PMC Article

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