Hyperthyroidism induced by Graves' disease reversibly affects skin microvascular reactivity

BACKGROUND: The impact of hyperthyroidism induced by Graves' disease (GD) on skin microcirculation has not been established. We aimed to assess vascular reactivity in hyperthyroid GD patients before and during treatment. METHODS: Laser Doppler flux (LDF) was measured in 31 newly diagnosed hyperthyroid GD patients with an increased TSH receptor stimulating antibody (TSAb) levels before the methimazole treatment; and again 5.8 +/- 0.8 months later when euthyroidism had been established; and in 30 healthy age- and gender-matched controls. Postocclusive reactive hyperaemia (PRH) was assessed by a 3-min occlusion of the brachial artery. RESULTS: Baseline LDF on the finger pulp and on the volar forearm were significantly higher in untreated GD patients compared to treated GD patients and controls (p < 0.05 for both). On the finger pulp, the time to maximal LDF during PRH was significantly shorter in untreated GD patients compared to controls (p < 0.05). On the forearm, the duration of PRH was significantly longer in untreated GD patients compared to controls (p < 0.05). Positive correlations of triiodothyronine and TSAb with some indices of PRH were established in treated GD patients. CONCLUSIONS: Hyperthyroidism induced by GD reversibly affects skin microcirculation, presumably by increasing the vasodilator capacity. Potential involvement of TSAb might be implicated.