Cardiovascular Disease Several epidemiological studies have examined for an association between subclinical hypothyroidism and the risk of cardiovascular outcomes. They have shown conflicting results due to differences in the demographic characteristics of patient populations, the study designs, and the TSH cut- off levels to define subclinical hypothyroidism. However, there is emerging evidence that patient age and TSH level have a major influence on the association. A meta- ana lysis of observational studies found a significant association between subclinical hypothyroidism and cardiovascular mortality in younger adult patients aged below 65 years (odds ratio (OR) 1.37; 95% confidence interval (CI) 1.04– 1.79) but the association was not seen in older patients. In fact, in very elderly patients above the age of 85 years, subclinical hypothyroidism has been shown to be associated with a decreased risk of cardiovascular and all- cause mortality. In another meta- analysis, which included more than 50 000 participants from 11 prospective cohorts, increasing TSH level in subclinical hypothyroidism was associated with a higher risk of fatal and non- fatal coronary heart disease events. This association was most striking in patients with TSH levels of 10 mU/ L or above, with hazard ratios of 1.89 (95% CI 1.28– 2.8) for non- fatal coronary heart disease events and 1.58 (95% CI 1.1– 2.27) for coronary heart disease deaths. In a meta- analysis of six prospective observational studies with over 25 000 participants, subclinical hypothyroidism was associated with a significantly higher risk of heart failure in patients with TSH levels of 10 mU/ L or above (hazard ratio 1.86; 95% CI 1.27– 2.72). In addition, patients with pre- existing heart failure may have a poorer prognosis in the presence of coexisting subclinical hypothyroidism. Finally, subclinical hypothyroidism has also been shown to be associated with several functional cardiovascular anomalies, including left ventricular diastolic dysfunction, reduced resting and exertional systolic function, increased vascular resistance, arterial stiffness, and endothelial dysfunction.

Cerebrovascular Disease

Like cardiovascular disease, the risk of cerebrovascular disease is increased in younger adult patients with subclinical hypothyroidism. A meta- analysis of 17 observational studies, which included over 47 000 participants, failed to demonstrate a significant increase in the risk of cerebrovascular events or fatal stroke in patients with subclinical hypothyroidism in the whole cohort. However, in younger patients under the age of 65 years, subclinical hypothyroidism was significantly associated with an increased risk of fatal stroke (HR 2.29; 95% CI 1.41– 3.74).

Adverse Metabolic Characteristics

Many observational studies have shown associations between subclinical hypothyroidism and several adverse metabolic parameters, which may partly explain the increased cardiovascular and cerebrovascular risk in younger patients with subclinical hypothyroidism. A meta- ana lysis of 16 observational studies, which included over 40 000 participants, found significantly increased levels of serum total cholesterol, low- density lipoprotein cholesterol and total triglyceride in patients with subclinical hypothyroidism as compared to euthyroid individuals although there was no difference in serum high- density lipoprotein cholesterol levels between the two groups [28]. The risk of adverse lipid profile increases with an increasing TSH level. In addition, there appears to be a gender- related difference in the relationship between subclinical hypothyroidism and adverse lipid profile, with a more pronounced effect in women. Apart from dyslipidaemia, a meta- ana lysis found an association between subclinical hypothyroidism and increased risks of type 2 diabetes (OR 1.93, 95% CI 1.66– 2.24) and its complications, including diabetic nephropathy (OR 1.74, 95% CI 1.34– 2.28), diabetic retinopathy (OR 1.42, 95% CI 1.21– 1.67), peripheral vascular disease (OR 1.85, 95% CI 1.35– 2.54) and peripheral neuropathy (OR 1.87, 95% CI 1.06– 3.28) [30]. Furthermore, subclinical hypothyroidism has been shown to be associated with a higher levels of plasma homocysteine (a risk factor for atherosclerosis) and insulin resistance as measured by homeostatic index of insulin resistance (HOMA- IR). Finally, a meta- analysis has also shown an association between subclinical hypothyroidism and non- alcoholic steatohepatitis (OR 1.63, 95% CI 1.19– 2.24).

Impaired Cognitive Function

Several studies have assessed for an association between subclinical hypothyroidism and impaired cognitive function showing inconsistent results. Two meta- analyses found no significant association between subclinical hypothyroidism and decline in cognitive function, as measured by Mini- Mental State Examination (MMSE) score. However, another meta- analysis has suggested that subclinical hypothyroidism is associated with an increased risk of impaired cognitive function and dementia in younger patients aged less than 75 years, particularly in those with higher TSH levels. These observations suggest more research is needed to conclude whether subclinical hypothyroidism increases the risk of cognitive decline.

Bone Loss, Osteoporotic Fractures, and Frailty

Although optimum thyroid function is important for bone health, subclinical hypothyroidism has not been shown to be associated with an increased risk of bone loss or osteoporotic fractures. Likewise, subclinical hypothyroidism is not associated with an increased risk of frailty in elderly populations.

Mood, Mental Health, and Well- Being

 Some studies have suggested that subclinical hypothyroidism is as sociated with poor neuropsychological function, mood, and quality of life. However, the association remains uncertain as other studies have failed to confirm these observations.

In summary, subclinical hypothyroidism is associated with a higher risk of cardiovascular and cerebrovascular disease in younger adult patients (below the age of 65 years), particularly in those with TSH levels of 10 mU/ L or above. This association may be partly explained by an increased prevalence of dyslipidaemia, type 2 diabetes, and other adverse metabolic characteristics in patients with subclinical hypothyroidism. In contrast, there is no convincing evidence to support the association between subclinical hypothyroidism and impaired cognitive function, osteoporosis, frailty, poor neuropsychological function, or reduced quality of life.

اخر الاخبار

اخبار العتبة العباسية المقدسة

قسم التطوير يقدم دورة عن أخلاقيات المهنة ضمن برنامج تأهيل المنتسبين الجدد

ضمن برنامج (وفاءً للدماء).. المجمع العلمي يقيم محفلًا قرآنيًّا في محافظة المثنى

قسم الشؤون الفكرية يرفد المكتبة المركزية في ديالى بإصدارات معرفية

قسم التطوير يبحث مع ديوان الوقف الشيعي آفاق التعاون في مجال التدريب والتطوير المؤسسي

المزيد

الآخبار الصحية

خبير يكشف 5 حقائق طبية صادمة وغير معروفة

ليس الأسود ولا الحيتان.. "كائن صغير" هو أخطر قاتل للبشر!

بارقة أمل لمرضى "الإيدز".. علاج خلوي ينجح في كبح الفيروس

ظاهرة مقلقة تتوسع.. "المستنشقات" خطر صامت يهدد المراهقين

المزيد

الآخبار التكنلوجية

اكتشاف مادة في الثوم تحسن قوة العضلات وتبطئ شيخوختها

تطور الحياة على الأرض المبكرة اعتمد على معدن نادر

باحثون صينيون يطوّرون بطارية مائية قد تعمل 300 عام

الذكاء الاصطناعي..هل يصبح متهما جنائيا في الجرائم والانتحار؟

المزيد

مواضيع ذات صلة

Management of Subclinical Hypothyroidism - efficacy of Levothyroxine Treatment

Myxoedema Coma: Thyroid Hormone Therapy

Myxoedema Coma: Hyponatraemia

Diagnosis of Myxoedema Coma

Pathophysiology of Unstable Hemoglobin Disorders

Central Hypothyroidism

Severe Iodine Deficiency and natural Goitrogens

Iatrogenic Hypothyroidism

Pathobiology of Sickle Cell Disease: The Basis of Phenotypic Diversity

The Unique Systems Biology of Sickle Cell Anemia

Abnormalities of Sickle Red Blood Cells

Abnormal Molecular Behaviors of Sickle Hemoglobin