[Impairment of muscle vasodilation during mental stress in women with subclinical hypothyroidism].

Objective: To test the hypothesis that women with subclinical hypothyroidism (SH) have forearm vascular conductance (FVC) impaired during mental stress.

Subjects and methods: We evaluated 20 women with SH and 21 euthyroid (Control group), matched for age (p = 0.699) and body mass index (p = 0.462). Muscle blood flow (MBF) was assessed by venous occlusion plethysmography and blood pressure by Dixtal2023. Both variables were recorded simultaneously for 3 minutes of baseline followed by 3 minutes of mental stress. The FVC was calculated by dividing MBF by mean arterial pressure. Significant differences were assumed at p < 0.05.

Results: The SH group had higher concentrations of thyroid stimulating hormone (7.57 ± 3.17 vs. 2.10 ± 0,88 mU/L, p < 0.001). At baseline, the SH and control groups were similar for MBF (2.50 ± 0.79 vs. 2.55 ± 0,71 mL/ min/100 mL, p = 0.905, respectively) and FVC (2.80 ± 0.90 vs. 2.92 ± 0.88 units, p = 0.952, respectively). Throughout the mental stress test the SH and Control groups increased the MBF (time effect, p < 0.001) and FVC (time effect, p < 0.001) compared to baseline protocol. However, these variables were lower in SH group during the first (MBF: 3.66 ± 0.96 vs. 4.66 ± 1,61 mL/min/100 mL, p = 0.018, FVC: 3.95 ± 1.08 vs. 5.19 ± 1,96 units, p = 0.010) and second (MBF: 3.55 ± 1.01 vs. 4.62 ± 2,27 mL/min/100 ml, p = 0.018; FVC: 3.75 ± 1.07 vs. 4.92 ± 2,37 units, p = 0.020) minutes of mental stress test.

Conclusion: Women with SH have reduced muscle vasodilatatory response during mental stress.