Impairment of cutaneous microcirculation and vasoreactivity in primary hypothyroidism

The aim of this study was to identify potential diagnostic markers of microcirculation disorders in patients with primary hypothyroidism. Materials and methods This 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. Results The 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). Conclusion Overt 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.