Objective: Subclinical hypothyroidism affects 5-15% of the population and is associated with increased cardiovascular morbidity, although this is controversial. We recently reported a significant increase in brachial-ankle pulse wave velocity (baPWV), a parameter of arterial stiffening and an independent predictor for cardiovascular events, in subclinical hypothyroidism. The current study was performed to assess changes in enhanced baPWV in subclinical hypothyroidism during normalization of thyroid function.
Methods: Forty-two subclinical hypothyroid patients (male/female ratio 8/34) were monitored for changes in baPWV before and after levothyroxine (L-T(4)) replacement therapy.
Results: After attaining euthyroidism, 59.5% and 40.5% of the patients showed reduction and increase of baPWV, respectively. Baseline baPWV and pulse pressure were significantly higher in patients with reduced baPWV (1940.3+/-126.4 vs. 1726.4+/-110.4 cm/s, P=0.046; 62.1+/-3.1 vs. 50.7+/-3.7 mmHg, P=0.026, respectively). Baseline baPWV was significantly correlated with baseline pulse pressure in both groups, but the change in baPWV was significantly correlated with baseline pulse pressure only in patients with reduced baPWV (rho=-0.522, P=0.046). The male/female ratio was significantly lower in patients with reduced baPWV (4/21 vs. 7/10), and systolic, diastolic and pulse pressures and pulse rate decreased significantly only in patients with reduced baPWV.
Conclusions: Our results suggest that L-T(4) replacement therapy may be especially beneficial in female subclinical hypothyroid patients with high baseline baPWV and pulse pressure. The beneficial effects of L-T(4) replacement therapy in decreasing arterial stiffening and thus preventing cardiovascular disease might be limited to this sub-population.