Subclinical Hypothyroidism and Cardiovascular Risk – An Overview of Current Understanding

Subclinical or mild hypothyroidism is often associated with adverse cardiovascular risk factors, such as high cholesterol, together with hypertension, endothelial dysfunction and other atherosclerotic cardiovascular risk factors. The ischaemic abnormalities are probably related to long-term consequences of a slowly progressing development of hypothyroidism. In recent years, it has become evident that a consensus on the exact limits for cut-off between normal and subclinically hypothyroid individuals is not currently possible. The main reasons for this are differences for measurement of serum thyroid-stimulating hormone (TSH), that reference populations are very different and that a person’s intra-individual variability is much narrower than any population-based interval. Finally, the prevalence of subclinical hypothyroidism varies from 4 to 17% in different normal populations. Available evidence indicates that patients with subclinical hypothyroidism have developed or are at risk of developing an adverse cardiovascular profile and subclinical hypothyroidism is most likely a mild variant of overt hypothyroidism. There is currently no evidence for a treatment benefit, but studies to demonstrate the expected minor improvements have not been performed on a sufficiently large scale. Patients should be informed about the disease and based on a combined clinical and laboratory judgement, should be offered a therapeutic trial in case of even vague symptoms.

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Subclinical Hypothyroidism and Cardiovascular Risk—An Overview of Current Understanding

US Endocrinology ◽

10.17925/use.2010.06.1.92 ◽

2010 ◽

Vol 06 (01) ◽

pp. 92 ◽

Cited By ~ 1

Author(s):

Ulla Feldt-Rasmussen ◽

Keyword(s):

Risk Factors ◽

Cardiovascular Risk ◽

Cardiovascular Risk Factors ◽

Subclinical Hypothyroidism ◽

Large Scale ◽

Thyroid Stimulating Hormone ◽

Individual Variability ◽

Overt Hypothyroidism ◽

Therapeutic Trial ◽

Treatment Benefit

Subclinical or mild hypothyroidism is often associated with adverse cardiovascular risk factors, such as high cholesterol, together with hypertension, endothelial dysfunction and other atherosclerotic cardiovascular risk factors. The ischemic abnormalities are probably related to long-term consequences of a slowly progressing development of hypothyroidism. In recent years, it has become evident that a consensus on the exact limits for cut-off between normal and subclinically hypothyroid individuals is not currently possible. The main reasons for this are differences for measurement of serum thyroid-stimulating hormone (TSH), that reference populations are very different, and that a person’s intra-individual variability is much narrower than any population-based interval. Finally, the prevalence of subclinical hypothyroidism varies from 4 to 17% in different normal populations. Available evidence indicates that patients with subclinical hypothyroidism have developed or are at risk for developing an adverse cardiovascular profile, and subclinical hypothyroidism is most likely a mild variant of overt hypothyroidism. There is currently no evidence for a treatment benefit, but studies to demonstrate the expected minor improvements have not been performed on a sufficiently large scale. Patients should be informed about the disease and, based on a combined clinical and laboratory judgement, should be offered a therapeutic trial in case of even vague symptoms.

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Specific impact of cardiovascular risk factors on coronary microcirculation in patients with subclinical hypothyroidism

Journal of Medical Biochemistry ◽

10.5937/jomb0-34545 ◽

2021 ◽

Author(s):

Mirjana Stojković ◽

Biljana Nedeljković-Beleslin ◽

Milorad Tesic ◽

Zoran Bukumiric ◽

Jasmina Ciric ◽

...

Keyword(s):

Risk Factors ◽

Cardiovascular Risk ◽

Thyroid Hormones ◽

Cardiovascular Risk Factors ◽

Subclinical Hypothyroidism ◽

Thyroid Stimulating Hormone ◽

Normal Serum ◽

Free Triiodothyronine ◽

Flow Reserve ◽

The Impact

Background: Although thyroid hormones have significant effect on cardiovascular system, the impact of subtle thyroid dysfunction such as subclinical hypothyroidism (SCH) remains to be determined. We investigated coronary flow reserve (CFR) in patients with subclinical hypothyroidism. Methods: Thirty-two subjects with SCH and eighteen control subjects with normal serum thyroid hormones and thyroid-stimulating hormone (TSH) levels were included in the study. TSH, free thyroxine, free triiodothyronine, glucose, insulin, HbA1c, cholesterol, triglyceride and plasma levels of C-reactive protein were measured. Coronary diastolic peak flow velocities in left anterior descending coronary artery were measured at baseline and after adenosine infusion. CFR was calculated as the ratio of hyperemic to baseline diastolic peak velocity. Results: CFR values were not significantly different between the two groups (SCH 2.76 ± 0.35 vs controls 2.76 ± 0.42). There was a significant correlation of CFR with waist to hip ratio, hypertension, smoking habits, markers of glucose status (glucose level, HbA1c, insulin level, HOMA IR), cholesterol, LDL-cholesterol and triglyceride levels in SCH group, whereas only cholesterol level showed significant correlation with CFR in controls. There was no correlation between CFR and thyroid hormones. Conclusion: We concluded that there is a different impact of cardiovascular risk factors on CFR in SCH patients compared to healthy control and that these two groups behave differently in the same circumstances under the same risk factors. The basis for this difference could be that the altered thyroid axis “set point” changes the sensitivity of the microvasculature in patients with SCH to known risk factors.

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The relationship between serum thyroid-stimulating hormone, insulin resistance, and cardiovascular risk factors in obese patients with subclinical hypothyroidism

INTERNATIONAL JOURNAL OF ENDOCRINOLOGY ◽

10.22141/2224-0721.16.8.2020.222879 ◽

2021 ◽

Vol 16 (8) ◽

pp. 630-635

Author(s):

N.V. Pasiechko ◽

Yu.V. Yevstratieva

Keyword(s):

Risk Factors ◽

Insulin Resistance ◽

Cardiovascular Risk ◽

Cardiovascular Risk Factors ◽

Subclinical Hypothyroidism ◽

Thyroid Stimulating Hormone ◽

Obese Patients ◽

Obese People ◽

The Relationship ◽

Tsh Levels

Background. The epidemic of overweight and obesity presents a major challenge to chronic disease prevention and health across the life course around the world. The putative relationships between thyroid hormones, body weight, and adipose tissue homeostasis have been the focus of several studies in recent years, but the causal relationships between these parameters have not been well established. The purpose of the study: to investigate the relationship between serum thyroid-stimulating hormone (TSH), insulin resistance (IR), and cardiovascular risk factors in a sample of obese people with subclinical hypothyroidism. Materials and methods. A retrospective, longitudinal analysis of 145 obese patients was performed. The TSH and free thyroxine (fT4) levels, anthropometric measurements, and laboratory test results were analyzed. Results. Twenty-three individuals presented with TSH levels above the normal level (subclinical hypothyroidism). Their waist circumference (WC) was significantly higher than that of euthyroid individuals. Serum TSH positively correlated with the homeostasis model assessment of insulin resistance (HOMA-IR) index, triglycerides, and high-density lipoprotein cholesterol (HDL-C). Using TSH and body mass index as independent variables, TSH levels were shown to be independently related to HOMA-IR (p = 0.002) and triglycerides (p = 0.006). Among euthyroid subjects, individuals with TSH values < 2.5 mIU/ml exhibited statistically significant decreases in waist-to-hip ratio, HDL-C levels, and HOMA-IR scores and a tendency toward lower WC values. Conclusions. Subclinical hypothyroidism in overweight and obese people appears to be associated with excess weight, especially visceral weight. In the present sample of obese patients, TSH levels appear to be associated with insulin resistance.

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Improved Cardiovascular Risk Factors Control Associated with a Large-Scale Population Management Program Among Diabetes Patients

The American Journal of Medicine ◽

10.1016/j.amjmed.2018.01.024 ◽

2018 ◽

Vol 131 (6) ◽

pp. 661-668 ◽

Cited By ~ 3

Author(s):

Jamal S. Rana ◽

Andrew J. Karter ◽

Jennifer Y. Liu ◽

Howard H. Moffet ◽

Marc G. Jaffe

Keyword(s):

Risk Factors ◽

Cardiovascular Risk ◽

Cardiovascular Risk Factors ◽

Large Scale ◽

Population Management ◽

Management Program ◽

Scale Population ◽

Diabetes Patients

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Cardiovascular Risk Factors in Children and Adolescents with Subclinical Hypothyroidism: A protocol for meta-analysis and systematic review

10.37766/inplasy2020.4.0182 ◽

2020 ◽

Author(s):

Huan Deng ◽

Xian Wang ◽

Xianliang Qiu ◽

Qin Wen ◽

Shiyu Liu ◽

...

Keyword(s):

Risk Factors ◽

Systematic Review ◽

Cardiovascular Risk ◽

Children And Adolescents ◽

Cardiovascular Risk Factors ◽

Subclinical Hypothyroidism ◽

Meta Analysis

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Age-Related Serum Thyroid-Stimulating Hormone Reference Range in Older Patients Treated with Levothyroxine: A Randomized Controlled Feasibility Trial (SORTED 1)

European Thyroid Journal ◽

10.1159/000504047 ◽

2019 ◽

Vol 9 (1) ◽

pp. 40-48 ◽

Cited By ~ 1

Author(s):

Salman Razvi ◽

Vicky Ryan ◽

Lorna Ingoe ◽

Simon H. Pearce ◽

Scott Wilkes

Keyword(s):

Risk Factors ◽

Cardiovascular Risk ◽

Bone Resorption ◽

Cardiovascular Risk Factors ◽

Reference Range ◽

Thyroid Stimulating Hormone ◽

Adverse Impact ◽

Feasibility Trial ◽

Hypothyroid Patients ◽

Serum Tsh

Introduction: Serum thyroid-stimulating hormone (TSH) increases with age but target TSH is similar in younger and older hypothyroid patients on treatment. It is unknown if quality of life (QoL), hypothyroid symptoms and cardiovascular risk factors change in older hypothyroid patients treated to an age-appropriate reference range. Objective: To assess if a higher target serum TSH of 4.01–8.0 mU/L is feasible in, and acceptable to, older treated hypothyroid patients. Methods: A single-blind (participant) randomised controlled feasibility trial involving 48 hypothyroid patients aged ≥80 years on established and stable levothyroxine (LT4) therapy with serum TSH levels within the standard reference range (0.4–4.0 mU/L) was conducted. Standard (0.4–4.0 mU/L) or higher (4.1–8.0 mU/L) TSH target (standard TSH [ST] or higher TSH [HT] groups) LT4 for 24 weeks was administered. The outcome measures evaluated were thyroid function tests, QoL, hypothyroid symptoms, cardiovascular risk factors and serum marker of bone resorption in participants that completed the trial (n = 21/24 ST group, n = 19/24 HT group). Results: At 24 weeks, in the ST and HT groups, respectively, median (interquartile range) serum TSH was 1.25 (0.76–1.72) and 5.50 (4.05–9.12) mU/L, mean (± SD) free thyroxine (FT4) was 19.4 ± 3.5 and 15.9 ± 2.4 pmol/L, and daily LT4 dose was 82.1 ± 26.4 and 59.2 ± 23.9 µg. There was no suggestion of adverse impact of a higher serum TSH in the HT group with regard to any of the outcomes assessed. Conclusions: In hypothyroid patients aged ≥80 years on LT4 therapy for 24 weeks, there was no evidence that a higher target serum TSH was associated with an adverse impact on patient reported outcomes, cardiovascular risk factors or bone resorption marker over 24 weeks. Longer-term trials assessing morbidity and mortality outcomes and health-utility in this age group are feasible and should be performed.

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