Risk factors for cardiovascular disease in subclinical hypothyroidism

Hypothyroidism and Cardiovascular Disease: A Review

Hypothyroidism is an endocrine disorder more commonly in older adults. Simultaneously, this population has an increased incidence of cardiovascular risk factors and disease, which remains the leading cause of death worldwide. Thyroid hormones (THs) promote adequate function of the cardiovascular system as they exert their effects through receptors located in the myocardium and the vasculature. In hypothyroidism, this homeostasis is disrupted, which leads to the emergence of pathogenic pathways that accelerate the progression of cardiovascular disease and aggravate its outcomes in these individuals. This article has reviewed existing literature on the relationship between hypothyroidism and cardiovascular disease (CVD). We have explored the pathogenic mechanisms linking both conditions and highlighted the prevalence of cardiovascular risk factors as well as the increased incidence of cardiovascular events in overt and subclinical diseases. Furthermore, indications of hormone replacement therapy in subclinical disease and its efficacy in reducing CVD morbidities in a particular subset of patients have been discussed.

Clinical presentation and prognosis of COVID-19 in older adults with hypothyroidism: data from the GeroCovid observational study

BACKGROUND

The prevalence of hypothyroidism among older patients hospitalized for COVID-19 and its association with mortality is unclear. This study aims to investigate the prevalence of hypothyroidism in older COVID-19 inpatients and verify if this comorbidity is associated with a specific pattern of onset symptoms and a worse prognosis.

METHODS

COVID-19 inpatients aged ≥ 60 years, participating in the GeroCovid acute wards cohort, were included. The history of hypothyroidism was derived from medical records and the use of thyroid hormones. Sociodemographic data, comorbidities, symptoms/signs at the disease onset and inflammatory markers at ward admission were compared between people with vs without history of hypothyroidism. The association between hypothyroidism and in-hospital mortality was tested through Cox regression.

RESULTS

Of the 1245 patients included, 8.5% had a history of hypothyroidism. These patients were more likely to present arterial hypertension and obesity compared with those without an history of hypothyroidism. Concerning COVID-19 clinical presentation, patients with hypothyroidism had less frequently low oxygen saturation and anorexia but reported muscle pain and loss of smell more commonly than those without hypothyroidism. Among the inflammatory markers, patients with hypothyroidism had higher lymphocytes values. At Cox regression, hypothyroidism was associated with reduced in-hospital mortality only in the univariable model (HR = 0.66, 95% CI 0.45-0.96, p = 0.03); conversely, no significant result were observed after adjusting for potential confounders (HR = 0.69, 95% CI 0.47-1.03, p = 0.07).

CONCLUSIONS

Hypothyroidism does not seem to substantially influence the prognosis of COVID-19 in older people, although it may be associated with peculiar clinical and biochemical features at the disease onset.

Hypothyroidism does not lead to worse prognosis in COVID-19: findings from the Brazilian COVID-19 registry

BACKGROUND

It is not clear whether previous thyroid diseases influence the course and outcomes of COVID-19.

METHODS

The study is a part of a multicentric cohort of patients with confirmed COVID-19 diagnosis from 37 hospitals. Matching for age, sex, number of comorbidities, and hospital was performed for the paired analysis.

RESULTS

Of 7,762 patients with COVID-19, 526 had previously diagnosed hypothyroidism and 526 were matched controls. The median age was 70 years, and 68.3% were females. The prevalence of comorbidities was similar, except for coronary and chronic kidney diseases that were higher in the hypothyroidism group (p=0.015 and p=0.001). D-dimer levels were lower in patients with hypothyroid (p=0.037). In-hospital management was similar, but hospital length-of-stay (p=0.029) and mechanical ventilation requirement (p=0.006) were lower for patients with hypothyroidism. There was a trend of lower in-hospital mortality in patients with hypothyroidism (22.1% vs 27.0%; p=0.062).

CONCLUSION

Patients with hypothyroidism had a lower requirement of mechanical ventilation and showed a trend of lower in-hospital mortality. Therefore, hypothyroidism does not seem to be associated with a worse prognosis.

The association between subclinical hypothyroidism and metabolic syndrome: an update meta-analysis of observational studies

The association between subclinical hypothyroidism (SCH) and metabolic syndrome (MetS) has been widely discussed. This study aimed to conduct an update and comprehensive meta-analysis to reveal the risk of MetS and its components in SCH. PubMed, Embase and ISI Web of Knowledge were searched to identify relevant studies through February 20^th, 2020. Review Manager 5.3 and Stata 14.0 were used to conduct the meta-analysis. Both fixed-effects and random-effects models were used. In total, 18 articles (19 studies) incorporating 79,727 participants were included. The pooled OR for MetS comparing subjects with SCH with euthyroid subjects was 1.28 (95% CI: 1.19 to 1.39, p = 0.04, I² = 40%). Subgroup analysis results showed significant associations of SCH and MetS in the adult subgroup (OR = 1.28, 95% CI: 1.18-1.40), Asian population subgroup (OR = 1.30, 95% CI: 1.19-1.42) and cross-sectional study design subgroup (OR = 1.31, 95% CI: 1.16-1.47). Significant associations of SCH and MetS also existed in all MetS definition criteria subgroups except the Chinese Diabetes Society (CDS) subgroup. SCH was correlated with MetS and was not affected by the subgroup analysis stratified by the proportion of females in the total population, the TSH cutoff value in SCH diagnostic criteria, or the adjustment for confounding factors. SCH was identified to be associated with an increased risk of obesity, hypertension, high triglyceride (TG) levels and low high-density lipoprotein cholesterol (HDL-C) levels. In conclusion, SCH is significantly associated with an increased risk of MetS and four out of five components of MetS.

Extracellular Mitochondrial Components and Effects on Cardiovascular Disease

Besides being powerhouses of the cell, mitochondria released into extracellular space act as intercellular signaling. Mitochondria and their components mediate cell-to-cell communication in free form or embedded in a carrier. The pathogenesis of cardiovascular disease is complex, which shows close relationship with inflammation and metabolic abnormalities. Since mitochondria sustain optimal function of the heart, extracellular mitochondria are emerging as a key regulator in the development of cardiovascular disease. In this review, we provide recent findings in the presence and forms of mitochondria transfer between cells, as well as the effects of these mitochondria on vascular inflammation and ischemic myocardium. Mitochondrial transplantation is a novel treatment paradigm for patients suffering from acute cardiovascular accident and challenges the traditional methods of mitochondria isolation.

Physical activity in women with subclinical hypothyroidism

PURPOSE

Physical activity is associated with many health-related benefits. However, there is a shift towards inactive lifestyles around the world. Subclinical hypothyroidism (SCH) may have adverse effects similar to hypothyroidism. The presence of symptoms and reduced physical performance in SCH may contribute to an inactive lifestyle. Therefore, the present study aimed to compare physical activity levels (PALs) between women with subclinical hypothyroidism and healthy controls.

METHODS

Thirty-two women with newly diagnosed SCH and 28 healthy women were enrolled in this cross-sectional study. Arterial stiffness was evaluated by pulse wave velocity (PWV). Neuromuscular symptoms were questioned. Participants wore a physical activity monitor (SenseWear^® Armband) for 4 consecutive days. Handgrip and quadriceps muscle strength were assessed by dynamometer. Functional exercise capacity was assessed by 6-minute walk test (6MWT).

RESULTS

There was no significant difference in sociodemographic variables between the groups. PWV was significantly higher in the SCH group (P = 0.006). Physical activity duration and number of steps were significantly lower in the SCH group (P < 0.05). There was significant difference in neuromuscular symptoms, handgrip and quadriceps muscle strength, and 6MWT distance between the groups (P < 0.05).

CONCLUSIONS

This study demonstrates that women with SCH had lower PALs compared to healthy controls. Women with SCH should participate in exercise programs to increase physical activity and muscle strength to achieve adequate PALs.

Effect of radiotherapy on the expression of cardiovascular disease-related miRNA-146a, -155, -221 and -222 in blood of women with breast cancer

Breast cancer (BC) is one of the most important neoplasias among women. Many patients receive radiotherapy (RT), which involves radiation exposure of the thoracic zone, including the heart and blood vessels, leading to the development of cardiovascular disease (CVD) as a long-term side effect. The severity of CVD-related pathologies leads research on assessing novel CVD biomarkers as diagnostic, prognostic or therapeutic agents. Currently, the possible candidates include blood microRNAs (miRNAs). Previous studies have supported a role for miRNA-146a, -155, -221, and -222 in the progression of CVD. Our purpose was to evaluate the RT-induced modulation of the expression of these miRNAs in the blood of women with BC. Pre-RT control and post-RT blood samples were collected, and after miRNA isolation and reverse transcription, the levels of the selected miRNAs were measured by real-time PCR. Our results showed that miRNA-155 exhibited the lowest expression, while miRNA-222 exhibited the highest expression, followed by miRNA-221. The expression of each individual miRNA was positively correlated with that of the others both pre-RT control and post-RT and inversely correlated with age before RT. Furthermore, RT promoted the overexpression of the selected miRNAs. Their levels were also affected by CVD-linked clinical parameters, treatment and BC side. Modulation of the expression of the selected miRNAs together with other risk factors might be associated with the development of future cardiovascular pathologies. Further confirmatory studies are needed to assess their potential as possible biomarkers in the progression of or as therapeutic targets for RT-induced CVD in BC patients.

Intrauterine Zn Deficiency Favors Thyrotropin-Releasing Hormone-Increasing Effects on Thyrotropin Serum Levels and Induces Subclinical Hypothyroidism in Weaned Rats

Individuals who consume a diet deficient in zinc (Zn-deficient) develop alterations in hypothalamic-pituitary-thyroid axis function, i.e., a low metabolic rate and cold insensitivity. Although those disturbances are related to primary hypothyroidism, intrauterine or postnatal Zn-deficient adults have an increased thyrotropin (TSH) concentration, but unchanged thyroid hormone (TH) levels and decreased body weight. This does not support the view that the hypothyroidism develops due to a low Zn intake. In addition, intrauterine or postnatal Zn-deficiency in weaned and adult rats reduces the activity of pyroglutamyl aminopeptidase II (PPII) in the medial-basal hypothalamus (MBH). PPII is an enzyme that degrades thyrotropin-releasing hormone (TRH). This hypothalamic peptide stimulates its receptor in adenohypophysis, thereby increasing TSH release. We analyzed whether earlier low TH is responsible for the high TSH levels reported in adults, or if TRH release is enhanced by Zn deficiency at weaning. Dams were fed a 2 ppm Zn-deficient diet in the period from one week prior to gestation and up to three weeks after delivery. We found a high release of hypothalamic TRH, which along with reduced MBH PPII activity, increased TSH levels in Zn-deficient pups independently of changes in TH concentration. We found that primary hypothyroidism did not develop in intrauterine Zn-deficient weaned rats and we confirmed that metal deficiency enhances TSH levels since early-life, favoring subclinical hypothyroidism development which remains into adulthood.