OBJECTIVE: The aim of this study was to investigate aortic stiffness and left ventricular
(LV) systolic and diastolic function in patients with differentiated thyroid cancer
(DTC) on thyroxine (L-T4) therapy and after L-T4 withdrawal to assess the cardiovascular
impact of long-term subclinical hyperthyroidism and short-term overt hypothyroidism.
METHODS: Twenty-four patients who had had total thyroidectomy and radioiodine ablation
for differentiated thyroid cancer were studied on two occasions: on TSH suppressive
L-T4 therapy (sTSH 0.24 +/- 0.11 mU/L), and 4 weeks after L-T4 withdrawal (sTSH 89.82
+/- 29.36 mU/L). Echocardiography was performed and thyroid function, serum thyroglobulin,
lipid parameters, homocystine, C-reactive protein, fibrinogen and von Willebrand factor
activity (vWF) were measured. Twenty-two healthy volunteers matched for age and sex
served as euthyroid controls. RESULTS: Aortic stiffness was increased both in hypothyroidism
(6.04 +/- 2.88 cm2/dyn/103, p < 0.05) and subclinical hyperthyroidism (9.27 +/- 4.81
cm2/dyn/103, p < 0.05) vs. controls (3.92 +/- 1.84 cm2/dyn/103). Subclinical hyperthyroidism
had a more marked effect (p < 0.05). LV dimensions and ejection fractions were similar
before and after L-T4 withdrawal. The E'/A' was higher in euthyroid controls (1.34
+/- 1.02) as compared to both subclinical hyperthyroidism (1.0 +/- 0.14, p < 0.05)
and overt hypothyroidism (1.13 +/- 0.98, p < 0.05). Change of aortic stiffness correlated
with change of free-thyroxine (fT4), vWF and fibrinogen levels in a positive manner.
CONCLUSION: Long-term thyrotropin-suppression therapy has continuous adverse effects
on the arterial wall. The degree of TSH suppression in patients with DTC should be
kept at the possible minimum, based on individually determined potential benefits
and risks of treatment, especially in patients with cardiovascular co-morbidities.