Impairment of cutaneous microcirculation and vasoreactivity in primary hypothyroidism

The aimof this study was to identify potential diagnostic markers of microcirculation disorders in patients with primary hypothyroidism.Materials and methodsThis cross-sectional study included patients with overt (OH, n = 14) and subclinical (SH, n = 37) hypothyroidism, and healthy volunteers (HV, n = 50). Using laser Doppler flowmetry (LDF), mean cutaneous blood flow in the dorsal forearm was assessed at rest (M), during cooling to 10 °C (M_10°C), heating to 35 °C (M_35°C) and to 42 °C (M_42°C). The standard deviation (σ) and the coefficient of variation of cutaneous blood flow (Kv=σ/M) at rest were calculated. The amplitudes of microvascular blood flow oscillations in frequency ranges corresponding to the neurogenic, myogenic, respiratory, and pulse mechanisms of microcirculation modulation were also calculated (A_n, A_m, A_resp, A_card). Laboratory parameters were evaluated.ResultsThe OH group had reduced blood flow variability (σ) compared to the HV (p=0.025) and SH (p=0.037) groups. Kv was lower in OH compared to SH (p=0.041). Acard was decreased in the OH group compared to the HV (p=0.001) and SH (p=0.012) groups. M_42°C was reduced in OH compared to HV (p=0.014). Hypercholesterolemia and increased IL-6 were found in the OH and SH groups compared to HV. In OH, the red blood cell distribution width (RDW) was increased compared to HV (p=0.026).ConclusionOvert hypothyroidism is associated with decreased total and pulse variability of cutaneous microvascular blood flow, decreased cutaneous hyperemia during local heating to 42 °C, and increased RDW. These microcirculatory disorders are accompanied by hypercholesterolemia and increased IL-6 levels.