Clinical Hemorheology and Microcirculation 61 (2015) 459–470 DOI 10.3233/CH-141911 IOS Press
459
Hyperthyroidism induced by Graves’ disease reversibly affects skin microvascular reactivity Nataˇsa Bedernjak Bajuka , Katja Zaletela , Simona Gaberˇscˇ eka and Helena Lenasib,∗ a b
Department of Nuclear Medicine, University Medical Centre Ljubljana, Ljubljana, Slovenia Institute of Physiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
Abstract. 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. Keywords: Graves’ disease, hyperthyroidism, skin microcirculation, laser Doppler fluxmetry, postocclusive reactive hyperaemia
1. Introduction Clinical hyperthyroidism is characterised by increased thyroxine (T4 ) and/or triiodothyronine (T3 ) levels and a decreased thyroid stimulating hormone (TSH) level. The most frequent cause is Graves’ disease (GD) in which hyperthyroidism is induced by stimulating antibodies against the TSH receptor (TSAb). Patients frequently present with cardiovascular manifestations as thyroid hormones exert profound direct and indirect effects on the cardiovascular system and haemodynamics [16, 20, 38]. Hyperthyroidism increases basal metabolism and induces a hyperdynamic ‘high-output’ state as well as a marked decrease of peripheral vascular resistance. Apart from the indirect effects of increased oxygen consumption and heat production, changes of vascular resistance could be related to increased vascularity and/or to alterations of vascular control mechanisms [16, 20, 36]. However, the mechanisms of the thyroid ∗ Corresponding author: Helena Lenasi, Institute of Physiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia. Tel.: +386 15437513; Fax: +386 15437501; E-mail: [email protected].
1386-0291/15/$35.00 © 2015 – IOS Press and the authors. All rights reserved
460
N.B. Bajuk et al. / Hyperthyroidism and skin microvascular reactivity
hormones’ actions on the vasculature are poorly understood. The pattern and mechanisms of T3 actions might differ with respect to the vessel type [26, 36]. T3 has been shown to affect endothelial function by enhancing the expression of endothelial nitric oxide synthase (NOS), and increasing the endotheliumdependent vasodilation in isolated vessels [4, 16, 23, 36]. Separately, T3 has been suggested to directly target vascular smooth muscle cells (VSMC) by genomic and nongenomic mechanisms affecting ion currents through the plasma membrane [15]. Furthermore, T3 has been reported to stimulate neuronal and inducible NOS in VSMC independently of endothelium, leading to vascular relaxation [5]. In vivo human studies have shown that an acute infusion of T3 increased the endothelium-dependent vasodilation in healthy subjects without affecting the endothelium-independent vasodilation [26]. There are only two available studies on the impact of hyperthyroidism on human microcirculation [29, 37]. Weiss et al. only assessed baseline skin perfusion in hyperthyroid patients by the use of laser Doppler (LD) fluxmetry without any provocation test. They showed an increased LD flux (LDF) in patients compared to healthy subjects. After appropriate treatment when euthyroidism was restored, the values were comparable with healthy subjects [37]. On the other hand, Pazos-Moura et al. found no significant differences in the response of the nailfold microcirculation to a 1-min occlusion of the brachial artery in hyperthyroid patients; yet, they used the technique of dynamic capillaroscopy, which only evaluates the nutritive blood flow [29]. Therefore, we aimed to assess in vivo vascular reactivity in hyperthyroid GD patients, and to estimate the potential influence of treatment with antithyroid drugs on vascular reactivity in the same patients, who had achieved euthyroid state during treatment. Skin microcirculation was chosen as a model since it is easily accessible and potentially reflects generalized vascular function [12, 19]. Furthermore, it has been reported to be often compromised in different endocrine diseases [11, 24]. We hypothesized that hyperthyroidism would affect skin microcirculation as thyroid hormones increase the production of heat [33], whereas skin is the main organ for heat elimination in the human body [13]. We measured the skin blood flow (SkBF) by using LD fluxmetry. Although the object of some criticism [14, 19], especially considering the variability, LD fluxmetry could be regarded as a valuable tool for noninvasive estimation of cutaneous blood flow [19, 21, 34]. Vascular reactivity was assessed by studying postocclusive reactive hyperaemia (PRH), a transient increase of blood flow in response to a temporal occlusion of the corresponding artery. PRH [18, 21] has been frequently used as a measure of endothelial function in clinical practice [1, 19, 21].
2. Materials and methods 2.1. Study population In our prospective case-control study, GD patients and healthy controls were investigated. In the first group, 31 newly diagnosed hyperthyroid GD patients (mean duration of symptoms 2.7 ± 2.4 months; range 0.5–12) without concomitant diseases were recruited consecutively in the period from September 2012 to May 2013. GD was diagnosed by the presence of clinical and biochemical hyperthyroidism, a diffuse goitre with its characteristic ultrasound appearance, and increased TSAb. Then, patients were treated with methimazole until euthyroidism was restored. Five patients, in whom euthyroidism was not successfully restored, were excluded from the study. Therefore, the second group consisted of the remaining 26 methimazole-treated euthyroid GD patients, who were evaluated at a mean of 5.8 ± 0.8 months (range 3.8–7.2) after the beginning of treatment. The third group consisted of 30 age- and gender-
N.B. Bajuk et al. / Hyperthyroidism and skin microvascular reactivity
461
matched euthyroid healthy subjects in whom thyroid disease was excluded by a thyroid specialist. The study was approved by the national ethics committee and conducted according to the Declaration of Helsinki. Written informed consent was obtained from each subject. 2.2. Study design In each subject the following parameters were measured: heart rate, systolic and diastolic blood pressure at the brachial artery, body mass index (BMI), TSH, free T4 (fT4 ) and free T3 (fT3 ). In addition to these parameters, the GD patients were also measured for TSAb antibodies, which are distinctive for the disease and were determined at each occasion. In all subjects, vascular reactivity of the skin microcirculation was assessed using LD fluxmetry. Before the measurements, subjects were asked to fast, to not drink coffee, black tea or to smoke. The LDF measurements were performed in a quiet room with a temperature kept between 23◦ and 25◦ C. Prior to the measurements subjects had to lie in a supine position for 30 minutes to acclimatize. During the measurements, they were asked not to move. Baseline LDF was measured for five minutes on two representative measuring sites: the volar forearm and the finger pulp of the ipsilateral hand middle finger. These two sites are often tested as they differ in their anatomical and physiological organization. For the assessment of vascular reactivity, PRH was induced by a 3-min occlusion of the brachial artery. After the release of the occlusion we continued the measurements until baseline LDF was restored, and for five consecutive minutes thereafter. Simultaneously, skin temperature (T) was measured on the same sites as LDF. Throughout the experiment, electrocardiogram (ECG) and blood pressure of the digital artery were recorded. 2.3. Methods BMI at baseline was calculated according to the formula: weight/height2 (kg/m2 ). Blood pressure at the brachial artery was measured by the Riva-Rocci method. TSH concentration was measured by the TSH3-Ultra test using an analyzer ADVIA Centaur (Siemens Medical Solutions Diagnostics); reference values were between 0.55 to 4.78 mU/L. The concentrations of fT4 and fT3 were determined by an ADVIA Centaur analyzer (Siemens Medical Solutions Diagnostics) with reference values between 11.5 and 22.7 pmol/L and between 3.5 and 6.5 pmol/L, respectively. TSAb concentration was measured by a Kryptor compact plus analyzer (Brahms TRAK human Kryptor), where normal values were below 1.8 U/L. SkBF was measured with a two-channel LD fluxmeter Periflux P4001 Master/4002 (Perimed, Sweden) using a laser beam with a wavelength of 780 nm. The principles governing the measurement of skin perfusion with this method have been described elsewhere [14, 19, 34]. In brief, a laser beam is directed into the skin, where part of it reflects back from the moving erythrocytes. LD probes measure approximately one cubic millimeter of the skin tissue. The velocity of the blood flow is determined by using the Doppler effect, and the SkBF is expressed in arbitrary perfusion units (PU). Before the measurement, the device was calibrated for biological zero calibration. The LD probes were attached to the volar forearm (non-glabrous area), to the sites without visible cutaneous vessels, and to the pulp of the middle finger (glabrous area) of the ipsilateral hand. Vascular reactivity studies were performed by inducing PRH as described above. The sampling frequency was 500 Hz and the digitalized LDF signal was simultaneously transmitted to a personal computer for further analysis. Skin T was continuously recorded by a digital
462
N.B. Bajuk et al. / Hyperthyroidism and skin microvascular reactivity
thermometer (Peritemp PF4005, Perimed, Sweden); the T probes were fixed to the same spots under the LD probe holder. Arterial blood pressure (systolic, diastolic and mean) of the fourth finger of the hand was recorded on-line by the use of a Finapress device (Finapress, Ohmeda 2300). A standard ECG was continuously monitored through the standard second lead by a conventional ECG apparatus. 2.4. Data acquisition and statistical analysis The LDF data were analyzed by the Neurocard LDDA acquisition system (NeurocardTM LDDA, Meditronic, Germany). Baseline LDF was estimated by averaging the 5-min values. Accordingly, the skin T data were averaged. Also, the blood pressure data were averaged and the heart rate determined from the averaged RR interval of the ECG tracing. As for PRH, the following indices were determined: maximal LDF after the release of the occlusion, time to maximal LDF, relative increase of the LDF (% of baseline LDF) and net amplitude of the LDF increase after the release of the occlusion (determined by subtracting baseline LDF from maximal LDF), duration of PRH, area under the PRH curve (AUC) (determined as an integer of the LDF values over the time of the duration of PRH). Statistical analysis was performed using the Statistica software version 7.1 (StatSoft, Tulsa, OK, USA). The distribution fitting test was applied. The values are presented as means ± SD or median (inter-quartile range), when appropriate. Datasets were compared using the Student’s two-tailed t-test for variables with normal distribution or the Mann-Whitney U test when the distribution was not normal. Multiple comparisons of variables were performed using a one-way ANOVA or a Kruskal-Wallis ANOVA and median test where appropriate. Correlations were calculated using the Pearson correlation test. The threshold for statistical significance was considered to be p value of 0.05. 3. Results 3.1. Clinical characteristics and baseline haemodynamic parameters As presented in Table 1, the three groups did not differ with respect to age, gender, and BMI. The heart rate was significantly higher in untreated GD patients than in GD patients, who had become euthyroid by treatment (p < 0.001), and it was also significantly higher in both GD groups compared to controls (p < 0.001 for both). Brachial artery systolic blood pressure was significantly higher in the GD group compared to the controls (p < 0.05), whereas there were no differences in the diastolic blood pressure among the groups. Similarly, there were no differences in the digital artery blood pressure between the groups (data not shown). Before the treatment, the GD patients presented with significantly lower TSH and significantly higher fT4 and fT3 levels than the treated GD patients and controls (Table 1), whereas no significant differences regarding hormone levels were observed between the treated GD patients and the controls. TSAb levels were significantly higher in GD patients before the treatment than in the euthyroid treated GD patients (p < 0.001). Nevertheless, TSAb levels did not normalise in all treated euthyroid patients, as in 13 out of 26 (50%) treated patients TSAb concentration was still above the cut-off value, ranging between 2 and 54 U/L. Baseline LDF and the corresponding skin T are presented in Table 2. On the finger pulp, baseline LDF was significantly higher in the untreated GD group as compared to the control group and to the
N.B. Bajuk et al. / Hyperthyroidism and skin microvascular reactivity
463
Table 1 Clinical and biochemical parameters in GD patients and controls
Gender (f/m) Age (years) BMI (kg/m2 ) Heart rate (beats/min) Ps (mmHg) Pd (mmHg) TSH (mU/L) fT4 (pmol/L) fT3 (pmol/L) TSAb (U/L)
GD before treatment (n = 31)
GD after treatment (n = 26)
Controls (n = 30)
P
24/7 41.26 ± 13.86 23.42 ± 0.65 90.9 ± 9.9aa,b 127.5 ± 18.1a 71.0 ± 9.4 0.008 (0.008–0.008)aa,b 52.60 (41.10–66.90)aa,b 22.31 (17.43–30.8)aa,b 8.9 (4.0–14.0)b
20/6 40.00 ± 13.17 24.58 ± 4.10 73.0 ± 7.2aa 123.3 ± 17.4 76.3 ± 13.3 1.448 (0.758–1.908) 13.25 (11.70–14.90) 4.67 (4.35–4.94) 1.5 (1.0–4.0)
23/7 41.03 ± 9.05 23.90 ± 3.72 62.5 ± 12.7 116.8 ± 13.5 73.8 ± 9.3 1.389 (1.160–2.155) 14.22 (13.29–15.40) 4.92 (4.63–5.07) Not analyzed
0.998 0.92 0.518
459
Hyperthyroidism induced by Graves’ disease reversibly affects skin microvascular reactivity Nataˇsa Bedernjak Bajuka , Katja Zaletela , Simona Gaberˇscˇ eka and Helena Lenasib,∗ a b
Department of Nuclear Medicine, University Medical Centre Ljubljana, Ljubljana, Slovenia Institute of Physiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
Abstract. 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. Keywords: Graves’ disease, hyperthyroidism, skin microcirculation, laser Doppler fluxmetry, postocclusive reactive hyperaemia
1. Introduction Clinical hyperthyroidism is characterised by increased thyroxine (T4 ) and/or triiodothyronine (T3 ) levels and a decreased thyroid stimulating hormone (TSH) level. The most frequent cause is Graves’ disease (GD) in which hyperthyroidism is induced by stimulating antibodies against the TSH receptor (TSAb). Patients frequently present with cardiovascular manifestations as thyroid hormones exert profound direct and indirect effects on the cardiovascular system and haemodynamics [16, 20, 38]. Hyperthyroidism increases basal metabolism and induces a hyperdynamic ‘high-output’ state as well as a marked decrease of peripheral vascular resistance. Apart from the indirect effects of increased oxygen consumption and heat production, changes of vascular resistance could be related to increased vascularity and/or to alterations of vascular control mechanisms [16, 20, 36]. However, the mechanisms of the thyroid ∗ Corresponding author: Helena Lenasi, Institute of Physiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia. Tel.: +386 15437513; Fax: +386 15437501; E-mail: [email protected].
1386-0291/15/$35.00 © 2015 – IOS Press and the authors. All rights reserved
460
N.B. Bajuk et al. / Hyperthyroidism and skin microvascular reactivity
hormones’ actions on the vasculature are poorly understood. The pattern and mechanisms of T3 actions might differ with respect to the vessel type [26, 36]. T3 has been shown to affect endothelial function by enhancing the expression of endothelial nitric oxide synthase (NOS), and increasing the endotheliumdependent vasodilation in isolated vessels [4, 16, 23, 36]. Separately, T3 has been suggested to directly target vascular smooth muscle cells (VSMC) by genomic and nongenomic mechanisms affecting ion currents through the plasma membrane [15]. Furthermore, T3 has been reported to stimulate neuronal and inducible NOS in VSMC independently of endothelium, leading to vascular relaxation [5]. In vivo human studies have shown that an acute infusion of T3 increased the endothelium-dependent vasodilation in healthy subjects without affecting the endothelium-independent vasodilation [26]. There are only two available studies on the impact of hyperthyroidism on human microcirculation [29, 37]. Weiss et al. only assessed baseline skin perfusion in hyperthyroid patients by the use of laser Doppler (LD) fluxmetry without any provocation test. They showed an increased LD flux (LDF) in patients compared to healthy subjects. After appropriate treatment when euthyroidism was restored, the values were comparable with healthy subjects [37]. On the other hand, Pazos-Moura et al. found no significant differences in the response of the nailfold microcirculation to a 1-min occlusion of the brachial artery in hyperthyroid patients; yet, they used the technique of dynamic capillaroscopy, which only evaluates the nutritive blood flow [29]. Therefore, we aimed to assess in vivo vascular reactivity in hyperthyroid GD patients, and to estimate the potential influence of treatment with antithyroid drugs on vascular reactivity in the same patients, who had achieved euthyroid state during treatment. Skin microcirculation was chosen as a model since it is easily accessible and potentially reflects generalized vascular function [12, 19]. Furthermore, it has been reported to be often compromised in different endocrine diseases [11, 24]. We hypothesized that hyperthyroidism would affect skin microcirculation as thyroid hormones increase the production of heat [33], whereas skin is the main organ for heat elimination in the human body [13]. We measured the skin blood flow (SkBF) by using LD fluxmetry. Although the object of some criticism [14, 19], especially considering the variability, LD fluxmetry could be regarded as a valuable tool for noninvasive estimation of cutaneous blood flow [19, 21, 34]. Vascular reactivity was assessed by studying postocclusive reactive hyperaemia (PRH), a transient increase of blood flow in response to a temporal occlusion of the corresponding artery. PRH [18, 21] has been frequently used as a measure of endothelial function in clinical practice [1, 19, 21].
2. Materials and methods 2.1. Study population In our prospective case-control study, GD patients and healthy controls were investigated. In the first group, 31 newly diagnosed hyperthyroid GD patients (mean duration of symptoms 2.7 ± 2.4 months; range 0.5–12) without concomitant diseases were recruited consecutively in the period from September 2012 to May 2013. GD was diagnosed by the presence of clinical and biochemical hyperthyroidism, a diffuse goitre with its characteristic ultrasound appearance, and increased TSAb. Then, patients were treated with methimazole until euthyroidism was restored. Five patients, in whom euthyroidism was not successfully restored, were excluded from the study. Therefore, the second group consisted of the remaining 26 methimazole-treated euthyroid GD patients, who were evaluated at a mean of 5.8 ± 0.8 months (range 3.8–7.2) after the beginning of treatment. The third group consisted of 30 age- and gender-
N.B. Bajuk et al. / Hyperthyroidism and skin microvascular reactivity
461
matched euthyroid healthy subjects in whom thyroid disease was excluded by a thyroid specialist. The study was approved by the national ethics committee and conducted according to the Declaration of Helsinki. Written informed consent was obtained from each subject. 2.2. Study design In each subject the following parameters were measured: heart rate, systolic and diastolic blood pressure at the brachial artery, body mass index (BMI), TSH, free T4 (fT4 ) and free T3 (fT3 ). In addition to these parameters, the GD patients were also measured for TSAb antibodies, which are distinctive for the disease and were determined at each occasion. In all subjects, vascular reactivity of the skin microcirculation was assessed using LD fluxmetry. Before the measurements, subjects were asked to fast, to not drink coffee, black tea or to smoke. The LDF measurements were performed in a quiet room with a temperature kept between 23◦ and 25◦ C. Prior to the measurements subjects had to lie in a supine position for 30 minutes to acclimatize. During the measurements, they were asked not to move. Baseline LDF was measured for five minutes on two representative measuring sites: the volar forearm and the finger pulp of the ipsilateral hand middle finger. These two sites are often tested as they differ in their anatomical and physiological organization. For the assessment of vascular reactivity, PRH was induced by a 3-min occlusion of the brachial artery. After the release of the occlusion we continued the measurements until baseline LDF was restored, and for five consecutive minutes thereafter. Simultaneously, skin temperature (T) was measured on the same sites as LDF. Throughout the experiment, electrocardiogram (ECG) and blood pressure of the digital artery were recorded. 2.3. Methods BMI at baseline was calculated according to the formula: weight/height2 (kg/m2 ). Blood pressure at the brachial artery was measured by the Riva-Rocci method. TSH concentration was measured by the TSH3-Ultra test using an analyzer ADVIA Centaur (Siemens Medical Solutions Diagnostics); reference values were between 0.55 to 4.78 mU/L. The concentrations of fT4 and fT3 were determined by an ADVIA Centaur analyzer (Siemens Medical Solutions Diagnostics) with reference values between 11.5 and 22.7 pmol/L and between 3.5 and 6.5 pmol/L, respectively. TSAb concentration was measured by a Kryptor compact plus analyzer (Brahms TRAK human Kryptor), where normal values were below 1.8 U/L. SkBF was measured with a two-channel LD fluxmeter Periflux P4001 Master/4002 (Perimed, Sweden) using a laser beam with a wavelength of 780 nm. The principles governing the measurement of skin perfusion with this method have been described elsewhere [14, 19, 34]. In brief, a laser beam is directed into the skin, where part of it reflects back from the moving erythrocytes. LD probes measure approximately one cubic millimeter of the skin tissue. The velocity of the blood flow is determined by using the Doppler effect, and the SkBF is expressed in arbitrary perfusion units (PU). Before the measurement, the device was calibrated for biological zero calibration. The LD probes were attached to the volar forearm (non-glabrous area), to the sites without visible cutaneous vessels, and to the pulp of the middle finger (glabrous area) of the ipsilateral hand. Vascular reactivity studies were performed by inducing PRH as described above. The sampling frequency was 500 Hz and the digitalized LDF signal was simultaneously transmitted to a personal computer for further analysis. Skin T was continuously recorded by a digital
462
N.B. Bajuk et al. / Hyperthyroidism and skin microvascular reactivity
thermometer (Peritemp PF4005, Perimed, Sweden); the T probes were fixed to the same spots under the LD probe holder. Arterial blood pressure (systolic, diastolic and mean) of the fourth finger of the hand was recorded on-line by the use of a Finapress device (Finapress, Ohmeda 2300). A standard ECG was continuously monitored through the standard second lead by a conventional ECG apparatus. 2.4. Data acquisition and statistical analysis The LDF data were analyzed by the Neurocard LDDA acquisition system (NeurocardTM LDDA, Meditronic, Germany). Baseline LDF was estimated by averaging the 5-min values. Accordingly, the skin T data were averaged. Also, the blood pressure data were averaged and the heart rate determined from the averaged RR interval of the ECG tracing. As for PRH, the following indices were determined: maximal LDF after the release of the occlusion, time to maximal LDF, relative increase of the LDF (% of baseline LDF) and net amplitude of the LDF increase after the release of the occlusion (determined by subtracting baseline LDF from maximal LDF), duration of PRH, area under the PRH curve (AUC) (determined as an integer of the LDF values over the time of the duration of PRH). Statistical analysis was performed using the Statistica software version 7.1 (StatSoft, Tulsa, OK, USA). The distribution fitting test was applied. The values are presented as means ± SD or median (inter-quartile range), when appropriate. Datasets were compared using the Student’s two-tailed t-test for variables with normal distribution or the Mann-Whitney U test when the distribution was not normal. Multiple comparisons of variables were performed using a one-way ANOVA or a Kruskal-Wallis ANOVA and median test where appropriate. Correlations were calculated using the Pearson correlation test. The threshold for statistical significance was considered to be p value of 0.05. 3. Results 3.1. Clinical characteristics and baseline haemodynamic parameters As presented in Table 1, the three groups did not differ with respect to age, gender, and BMI. The heart rate was significantly higher in untreated GD patients than in GD patients, who had become euthyroid by treatment (p < 0.001), and it was also significantly higher in both GD groups compared to controls (p < 0.001 for both). Brachial artery systolic blood pressure was significantly higher in the GD group compared to the controls (p < 0.05), whereas there were no differences in the diastolic blood pressure among the groups. Similarly, there were no differences in the digital artery blood pressure between the groups (data not shown). Before the treatment, the GD patients presented with significantly lower TSH and significantly higher fT4 and fT3 levels than the treated GD patients and controls (Table 1), whereas no significant differences regarding hormone levels were observed between the treated GD patients and the controls. TSAb levels were significantly higher in GD patients before the treatment than in the euthyroid treated GD patients (p < 0.001). Nevertheless, TSAb levels did not normalise in all treated euthyroid patients, as in 13 out of 26 (50%) treated patients TSAb concentration was still above the cut-off value, ranging between 2 and 54 U/L. Baseline LDF and the corresponding skin T are presented in Table 2. On the finger pulp, baseline LDF was significantly higher in the untreated GD group as compared to the control group and to the
N.B. Bajuk et al. / Hyperthyroidism and skin microvascular reactivity
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Table 1 Clinical and biochemical parameters in GD patients and controls
Gender (f/m) Age (years) BMI (kg/m2 ) Heart rate (beats/min) Ps (mmHg) Pd (mmHg) TSH (mU/L) fT4 (pmol/L) fT3 (pmol/L) TSAb (U/L)
GD before treatment (n = 31)
GD after treatment (n = 26)
Controls (n = 30)
P
24/7 41.26 ± 13.86 23.42 ± 0.65 90.9 ± 9.9aa,b 127.5 ± 18.1a 71.0 ± 9.4 0.008 (0.008–0.008)aa,b 52.60 (41.10–66.90)aa,b 22.31 (17.43–30.8)aa,b 8.9 (4.0–14.0)b
20/6 40.00 ± 13.17 24.58 ± 4.10 73.0 ± 7.2aa 123.3 ± 17.4 76.3 ± 13.3 1.448 (0.758–1.908) 13.25 (11.70–14.90) 4.67 (4.35–4.94) 1.5 (1.0–4.0)
23/7 41.03 ± 9.05 23.90 ± 3.72 62.5 ± 12.7 116.8 ± 13.5 73.8 ± 9.3 1.389 (1.160–2.155) 14.22 (13.29–15.40) 4.92 (4.63–5.07) Not analyzed
0.998 0.92 0.518
