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06-04-2006 | Thyroid | Article

Increased arterial stiffness in subclinical hypothyroidism patients


Free abstract

UK scientists have found that patients with subclinical hypothyroidism (SCH) have increased central arterial stiffness, and that the condition can be effectively treated using thyroid hormone replacement therapy with L-thyroxine.

The researchers, from Cardiff University, explain in the Journal of Clinical Endocrinology & Metabolism that "SCH is associated with increased risk of cardiac disease," but they clarify, "its impact on arterial function is less clear."

Specifically, they comment, studies have demonstrated reduced velocities among SCH patients using tissue Doppler echocardiography (TDE), a technique that quantifies myocardial wall motion. However, TDE has not been used to investigate subclinical left ventricular (LV) dysfunction in SCH patients.

Lead investigator J Lazarus and colleagues therefore used TDE to examine the arterial, overall cardiac, and LV function of 19 women with SCH and compared measurements with those of 10 female controls.

They also assessed whether any improvement in cardiac functioning was observed among the patients with 24 weeks of L-thyroxine treatment. Doses of L-thyroxine began at 50 mcg and steadily increased to 150 mcg. The patients and controls were aged an average of 49 and 50 years, respectively.

Echocardiographic testing revealed that baseline measures of vascular function, such as augmentation gradients, were significantly elevated in individuals with SCH compared with controls, at 10.3 versus 8.0 mmHg.

The average heart rate corrected augmentation index was 26.7% in the patients versus 18.8% in the controls. Importantly, this value fell to 19.7% in the patients after treatment.

However, there were no differences between SCH patients and controls regarding resting global, regional LV or regional myocardial velocities during maximal stress, nor was there any effect of treatment on these parameters, Lazarus and co-workers note.

"Arterial stiffness was increased in SCH and improved with L-thyroxine, which may be beneficial, whereas myocardial functional reserve was similar to controls and remained unaltered after treatment," they conclude.