Subclinical Hypothyroidism and Cardiovascular Risk: Recommendations for Treatment

The Association Between Subclinical Hypothyroidism and Sleep Quality: A Population-Based Study

Background and Aim

The relationship between subclinical hypothyroidism (SHYPO) and sleep quality is still unclear. Our objective was to compare the sleep quality between SHYPO patients and a control group with normal thyroid function.

Methods

A total of 2224 patients with SHYPO and 12,622 euthyroid (EUTH) control group patients were included in the present study. The Pittsburgh Sleep Quality Index (PSQI) was used to assess sleep quality. The sleep outcomes were compared to explore the association between SHYPO and sleep quality. Furthermore, we tried to identify the risk factors of poor sleep in SHYPO patients.

Results

Compared to the EUTH control patients, SHYPO patients had a higher PSQI score (6.83 ± 2.67 vs 6.64 ± 2.63, p =0.004) and a higher proportion of poor sleepers (67.09% vs 64.75%, p =0.033). Moreover, subjects with SHYPO were associated with poorer sleep (Odd Ratio (OR) 1.120, 95% Confidence Intervals (CI) 1.016 to 1.235, p =0.023), longer sleep latency (OR 1.162, 95% CI 1.053 to 1.282, p =0.003), and shorter sleep duration (OR 1.148, 95% CI 1.019 to 1.293, p =0.023) after adjusting for potential confounders. Furthermore, we found that lower age, lower body mass index, and women were risk factors for poor sleep quality in SHYPO patients.

Conclusion

Our findings suggest a relationship between SHYPO and poor sleep quality in a large Chinese population.

Diffuse Myocardial Injuries are Present in Subclinical Hypothyroidism: A Clinical Study Using Myocardial T1-mapping Quantification

Subclinical hypothyroidism (SHT) is a common disorder that may represent early thyroid dysfunction and is related to adverse cardiovascular events. However, myocardial injuries induced by SHT are difficult to detect. Our previous study demonstrated that the cardiac magnetic resonance (CMR) myocardial longitudinal relaxation time (T1) mapping technique is a useful tool for assessing diffuse myocardial injuries in overt hypothyroidism patients. This study was designed to detect whether diffuse myocardial injuries were present in SHT by using the T1 mapping technique. We found that SHT participants had significantly increased native T1 values within four segments of the left ventricle (all p < 0.01), especially patients with thyroid-stimulating hormone (TSH) levels ≥10 µIU/mL, compared with those in the controls. In addition, the native T1 values were negatively correlated with free thyroxine (FT4) (r = −0.476, p = 0.003) and were positively correlated with TSH (r = 0.489, p = 0.002). Furthermore, left ventricular diastolic function estimated by the peak filling rate (PFR) was significantly lower in patients with TSH levels ≥10 µIU/mL than that in the controls (p < 0.05). In conclusion, diffuse myocardial injuries were present in SHT, and T1 mapping may be a useful tool for evaluating mild myocardial injuries in SHT at an early stage. Our study is the first to confirm myocardial injuries in SHT patients using T1 mapping.

Decreased baroreflex sensitivity is linked to the atherogenic index, retrograde inflammation, and oxidative stress in subclinical hypothyroidism

Purpose/aim of the study: The present study investigated the link of hyperlipidemia, inflammation and oxidative stress (OS) to cardiovascular (CV) risks in subclinical hypothyroidism (SCH).

MATERIALS AND METHODS

We enrolled 81 subclinical hypothyroid patients and 80 healthy subjects as control. Their CV and autonomic functions were assessed by spectral analysis of heart rate variability (HRV), continuous blood pressure variability (BPV) measurement and conventional autonomic function testing. Thyroid profile, lipid profile, immunological, inflammatory and OS markers were estimated and correlated with the baro-reflex sensitivity (BRS), the marker of sympathovagal imbalance (SVI) & CV risk.

RESULTS

Mean arterial pressure (MAP, P<0.0001), total peripheral resistance (TPR, P<0.0001), ratio of low-frequency to high-frequency power of HRV (LF-HF ratio) (P<0.0001) were significantly higher and BRS (P<0.0001) was significantly lower in SCH group than the control group. BRS significantly correlated with heart rate, MAP, LF-HF ratio, lipid risk factors, anti-thyroperoxidase antibody, thyroid-stimulating hormone, high-sensitive C-reactive protein (hsCRP), malondialdehyde (MDA) and SCH.

CONCLUSIONS

It was concluded that SVI is associated with SCH. Though dyslipidemia, inflammation and OS contributed to decreased BRS, SCH per se contributed maximally to it. Decreased BRS could be a physiological basis of increased CV risks in patients with SCH.

Pathological periodontal pockets are associated with raised diastolic blood pressure in obese adolescents

BACKGROUND

Obesity, a well-known risk factor for developing cardiovascular disease (CVD), is associated with chronic periodontitis in adults. This cross-sectional pilot study on obese adolescents was designed to investigate whether periodontal disease in terms of pathological periodontal pockets is associated with raised blood pressure and other risk markers for CVD.

METHODS

The study included 75 obese subjects between 12 to 18 years of age, mean 14.5. Subjects answered a questionnaire regarding health, oral hygiene habits and sociodemographic factors. A clinical examination included Visible Plaque Index (VPI %), Gingival inflammation (BOP %) and the occurrence of pathological pockets exceeding 4 mm (PD ≥ 4 mm). Blood serum were collected and analyzed. The systolic and diastolic blood pressures were registered.

RESULTS

Adolescents with pathological periodontal pockets (PD ≥ 4 mm; n = 14) had significantly higher BOP >25% (P = 0.002), higher diastolic blood pressure (P = 0.008), higher levels of Interleukin (IL)-6 (P < 0.001), Leptin (P = 0.018), Macrophage Chemoattractant Protein-1 (MCP-1) (P = 0.049) and thyroid stimulating hormone (TSH) (P = 0.004) in blood serum compared with subjects without pathological periodontal pockets (PD ≥ 4 mm; n = 61). The bivariate linear regression analysis demonstrated that PD ≥ 4 mm (P = 0.008) and systolic blood pressure (P < 0.001) were significantly associated with the dependent variable "diastolic blood pressure". The association between PD ≥ 4 mm and diastolic blood pressure remained significant (P = 0.006) even after adjusting for potential confounders BMI-sds, age, gender, mother's country of birth, BOP >25%, IL-6, IL-8, Leptin, MCP-1, TSH and total cholesterol in the multiple regression analysis.

CONCLUSION

In conclusion, this study indicates an association between pathological periodontal pockets and diastolic blood pressure in obese adolescents. The association was unaffected by other risk markers for cardiovascular events or periodontal disease. The results call for collaboration between pediatric dentists and medical physicians in preventing obesity development and its associated disorders.

[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.

Subclinical hypothyroidism and left ventricular mechanics: a three-dimensional speckle tracking study

CONTEXT

Subclinical hypothyroidism (SHT) is associated with left ventricular (LV) remodeling. The LV mechanics has not been previously assessed by two- and three-dimensional (2DE and 3DE) speckle tracking imaging in the SHT patients.

OBJECTIVES

The objective of the study was to investigate LV mechanics by 2DE and 3DE speckle tracking in the SHT patients and evaluate the influence of levothyroxine therapy on LV remodeling.

DESIGN

We conducted a prospective study. All SHT patients received levothyroxine therapy and were followed up for 1 year after the euthyroid state had been achieved.

SETTING

The study was performed at a university hospital.

PATIENTS

We included 54 untreated women with SHT and 40 healthy control women who were of similar age.

MAIN OUTCOME MEASURES

The 2DE strain and strain rates, 3DE volumes, 3DE strain, and thyroid hormones levels were assessed.

RESULTS

The 2DE LV longitudinal and circumferential strain and systolic and early diastolic strain rates were significantly decreased in the SHT patients before therapy in comparison with the controls or the SHT patients after therapy. The 3DE LV cardiac output and ejection fraction were significantly reduced in the SHT patients at baseline compared with the controls or patients after 1 year of treatment. The 3DE LV longitudinal and radial strains were significantly lower in the SHT group before treatment in comparison with the controls or patients after therapy, whereas the 3DE LV circumferential and area strains gradually increased from untreated SHT patients, among the treated SHT patients, to the controls.

CONCLUSION

SHT significantly affects LV deformation assessed by 2DE and 3DE speckle tracking. The improvement of LV mechanics after 1 year of levothyroxine treatment is significant but incomplete.

Associations between thyroid hormone levels and regional fat accumulation in euthyroid men

OBJECTIVE

Body adiposity, especially ectopic fat accumulation, has a range of metabolic and cardiovascular effects. This study aimed to investigate whether thyroid function is associated with various regional fat quantities in euthyroid subjects.

METHODS

A total of 100 euthyroid men (free triiodothyronine (fT3), 4.77±1.21 pg/ml; free thyroxine (fT4), 1.38±0.21 ng/dl; and TSH, 2.09±0.91 μIU/ml) were enrolled in this cross-sectional study. We measured accumulated regional fat using 64-slice multi-detector computed tomography. Multiple linear regression analysis was used to determine whether accumulated fat in each region was associated with clinical parameters after adjusting for age.

RESULTS

FT3 was inversely correlated with BMI (R=0.232, P=0.029) and LDL cholesterol level (R=0.277, P=0.019). FT4 was inversely correlated with waist circumference (R=0.350, P=0.008) and BMI (R=0.355, P0.001). In multiple linear regression analysis, fT3 and fT4 levels were significantly associated with pericardial fat volume (fT3: B=-0.079, 95% CI -0.142 to -0.017, P=0.013; fT4: B=-0.411, 95% CI -0.780 to -0.042, P=0.030) in euthyroid men, independent of age. FT3 level was inversely associated with intramuscular fat area (B=-0.059, 95% CI -0.106 to -0.011, P=0.016) and hepatic fat quantity (B=-0.237, 95% CI -0.441 to -0.033, P=0.024) in euthyroid men, independent of age.

CONCLUSIONS

In euthyroid men, low levels of fT3 and fT4 were significantly associated with increased pericardial fat volume and BMI.

Is pituitary TSH an adequate measure of thyroid hormone-controlled homoeostasis during thyroxine treatment?

OBJECTIVE

In recognition of its primary role in pituitary-thyroid feedback, TSH determination has become a key parameter for clinical decision-making. This study examines the value of TSH as a measure of thyroid hormone homoeostasis under thyroxine (T(4)) therapy.

DESIGN AND METHODS

We have examined the interrelationships between free triiodothyronine (FT(3)), free T(4) (FT(4)) and pituitary TSH by means of i) a retrospective analysis of a large clinical sample comprising 1994 patients either untreated or on varying doses of l-T(4) and ii) independent mathematical simulation applying a model of thyroid homoeostasis, together with a sensitivity analysis.

RESULTS

Over a euthyroid to mildly hyperthyroid functional range, we found markedly different correlation slopes of log TSH vs FT(3) and FT(4) between untreated patients and l-T(4) groups. Total deiodinase activity (G(D)) was positively correlated with TSH in untreated subjects. However, G(D) was significantly altered and the correlation was lost under increasing l-T(4) doses. Ninety-five per cent confidence intervals for FT(3) and FT(4), when assessed in defined TSH concentration bands, differed significantly for l-T(4)-treated compared with untreated patients. Higher doses were often needed to restore FT(3) levels within its reference range. Sensitivity analysis revealed the influence of various structural parameters on pituitary TSH secretion including an important role of pituitary deiodinase type 2.

CONCLUSION

The data reveal disjoints between FT(4)-TSH feedback and T(3) production that persist even when sufficient T(4) apparently restores euthyroidism. T(4) treatment displays a compensatory adaptation but does not completely re-enact normal euthyroid physiology. This invites a study of the clinical consequences of this disparity.