Age and gender substantially influence the relationship between thyroid status and the lipoprotein profile: results from a large cross-sectional study

TSH is independently associated with remnant cholesterol in euthyroid adults: a cross-sectional study based on 29,708 individuals

PURPOSE

The study aims to investigate the relationship between thyroid-stimulating hormone (TSH) and remnant cholesterol (RC) in euthyroid adults.

METHODS

The adults who were recruited for the study had undergone physical examination at Beijing Chao-Yang Hospital. High RC levels were defined as the upper quartile of RC levels in males and females, respectively. The relationship between TSH and RC was assessed using the logistic and linear regression models.

RESULTS

A total of 29,708 adults (14,347 males and 15,361 females) were enrolled in this study. RC ≥ 0.77 mmol/L in males and RC ≥ 0.60 mmol/L in females were defined as high RC levels. With increasing serum TSH levels, the percentage of adults with high RC levels increased. The odds ratios (ORs (95% confidence intervals (CIs)) for high RC levels increased as TSH quartiles (Q) rose after full adjustments [males: Q2 1.11 (1.00-1.24), P < 0.05; Q3 1.03 (0.92-1.15), P > 0.05; Q4 1.25 (1.12-1.40), P < 0.001; and females: Q2 1.07 (0.96-1.20), P > 0.05; Q3 1.17 (1.05-1.31), P < 0.01, Q4 1.33 (1.20-1.48), P < 0.001, all P for trend < 0.001], using Q1 as the reference.

CONCLUSION

Higher TSH levels were independently associated with higher RC levels in euthyroid adults, this underscoring the significance of regulating TSH levels appropriately.

Relationship Between Serum Thyrotropin Levels and Metabolic Diseases in Older Adults

CONTEXT

Subclinical hypothyroidism is associated with metabolic diseases; however, it remains controversial in older individuals.

OBJECTIVE

This work aimed to investigate the relationship between thyrotropin (TSH) levels and metabolic diseases.

METHODS

In this cross-sectional study, sampling was conducted from nationally representative general communities from 31 provinces in mainland China. A total of6791 older (aged ≥65 years) and 55 303 young participants (aged 18-64 years) were selected after excluding individuals with overt hyperthyroidism or overt hypothyroidism. According to the kit, TSH reference range (0.27-4.2 mU/L) and the age-specific TSH range previously formulated (an upper limit of 8.86 mU/L for older adults and 6.57 mU/L for young adults), the older adults and young adults were separately divided into 4 groups based on their TSH levels. Main outcome measures included anthropometric assessments, serum concentrations of thyroid functions, and various metabolic parameters.

RESULTS

In contrast to young adults, there was no significant increase in the prevalence of any metabolic disorders assessed in the slightly elevated TSH group (TSH 4.21-8.86 mU/L) compared to the euthyroid group (TSH 0.27-4.2 mU/L) among older adults. After adjusting for interference factors, a TSH level higher than 8.86 mU/L was found to be an independent risk factor for low high-density lipoprotein cholesterol (OR, 1.84; 95% CI, 1.14-2.98) and dyslipidemia (OR, 1.49; 95% CI, 1.09-2.04) when compared to the euthyroid group in older adults.

CONCLUSION

Slightly elevated TSH levels are not associated with an increased risk of metabolic diseases in older adults. Therefore, we recommend raising the upper limit of the TSH range for individuals aged 65 years and older.

Association between sensitivity to thyroid hormones and dyslipidemia in patients with coronary heart disease

BACKGROUND

Thyroid hormones affect lipid metabolism via central and peripheral regulation. However, there have been few studies on the association between thyroid hormone sensitivity and dyslipidemia. We aimed to investigate the association between thyroid hormone sensitivity and dyslipidemia in patients with coronary heart disease (CHD).

METHODS

A total of 31,678 patients with CHD were included in this large multicenter retrospective study. Central thyroid hormone sensitivity was evaluated using the thyroid feedback quantile-based index (TFQI), parametric thyroid feedback quantile-based index (PTFQI), thyroid-stimulating hormone index (TSHI), and thyrotropin thyroxine resistance index (TT4RI); peripheral thyroid hormone sensitivity was assessed by the ratio of free triiodothyronine (FT3)/free thyroxine (FT4). Logistic regression analysis was used to analyze the association between thyroid hormone sensitivity and dyslipidemia.

RESULTS

Among 31,678 participants, 21,648 (68.34%) had dyslipidemia. In the multi-adjusted models, the risk of dyslipidemia was positively correlated with TFQI (odds ratio [OR]: 1.04; 95% confidence interval [CI]: 1.03-1.05), PTFQI (OR: 1.09; 95% CI: 1.06-1.12), TSHI (OR: 1.08; 95% CI: 1.06-1.11), and TT4RI (OR: 1.08; 95% CI: 1.05-1.11). Conversely, the risk of dyslipidemia was negatively correlated with FT3/FT4 (OR: 0.94; 95% CI: 0.92-0.97). In stratified analyses, the association between thyroid hormone sensitivity and dyslipidemia was statistically significant for different sexes, glucose levels, and blood pressure states.

CONCLUSION

There is a significant association between sensitivity to thyroid hormones and dyslipidemia, regardless of sex, glucose level, or blood pressure. Graphical abstract.

The relationships between thyroid functions of short-term rapid hypothyroidism and blood lipid levels in post-thyroidectomy patients of differentiated thyroid cancer

Objective

To explore the relationship between short-term rapid hypothyroidism and blood lipid levels in patients with differentiated thyroid cancer (DTC).

Methods

Seventy-five DTC patients scheduled to receive radioactive iodine ablation were enrolled. Levels of thyroid hormone and serum lipids were tested at two time points: the euthyroid before thyroidectomy, and the hypothyroid (off thyroxine). Then the collected data were analyzed.

Results

Totally 75 DTC patients enrolled, among them, 5o were female (66.67%) and 25 were male (33. 33%), with an average age of 52.24 ± 1.24 years old. The short-term rapid severe hypothyroidism induced by thyroid hormone withdrawal significantly aggravated dyslipidemia, particularly in patients with dyslipidemia before thyroidectomy (All P < 0.01). However, there was no significant differences between blood lipid levels with different thyroid stimulating hormone (TSH) levels. And our study showed significant negative correlations between free triiodothyronine levels and the changes from euthyjroidism to hypothyroidism in total cholesterol (r=-0.31, P=0.03), triglycerides (r=-0.39, P=0.006), high density lipoprotein-cholesterol (HDL-C) (r=-0.29, P=0.042), and significant positive correlations between free thyroxine and the changes of HDL-C (r=-0.32, P=0.027) were identified in females, however, which were not observed in males.

Conclusion

Short-term rapids severe hypothyroidism caused by thyroid hormone withdrawal can lead to rapid significant changes in blood lipid levels. It is necessary to pay attention to dyslipidemia and its long-term effects after thyroid hormone withdrawal, especially in patients with dyslipidemia before thyroidectomy.

Clinical trial registration

https://clinicaltrials.gov/ct2/show/NCT03006289?term=NCT03006289&draw=2&rank=1, identifier NCT03006289.

Sex-specific Association of Subclinical Hypothyroidism With Incident Metabolic Syndrome: A Population-based Cohort Study

OBJECTIVE

Subclinical hypothyroidism is known to increase the risk of cardiovascular diseases and mortality. However, the longitudinal association between subclinical hypothyroidism and incident metabolic syndrome remains unclear.

METHODS

A total of 3615 participants from Beijing Health Management Cohort were enrolled from 2012 to 2014 and followed through 2019. People were placed into subclinical hypothyroidism and euthyroidism groups according to serum-free thyroxine and TSH concentrations. We used Cox proportional hazards regression models to investigate the relationship between TSH level and incident metabolic syndrome considering the modification effect of sex and age.

RESULTS

Of 3615 participants, 1929 were men (53.4%); mean (SD) age was 43.51 (11.73) years. Throughout the follow-up (median [interquartile range], 3.0 [2.8-3.2] years), 738 individuals developed metabolic syndrome. Subclinical hypothyroidism was significantly associated with metabolic syndrome development only in men, and the adjusted hazard ratio was 1.87 (95% CI, 1.21-2.90) compared with euthyroidism group. Of note, there was no increased risk of metabolic syndrome in people aged 50 years or older with subclinical hypothyroidism.

CONCLUSIONS

Subclinical hypothyroidism is associated with incident metabolic syndrome in young men. Further studies are needed to evaluate the targeted threshold and benefit of thyroid hormone replacement therapy for metabolic health.

Menopausal Impact on the Association Between Thyroid Dysfunction and Lipid Profiles: A Cross-Sectional Study

BACKGROUND

Both dyslipidemia and thyroid dysfunction have a high prevalence rate and are important risk factors for cardiovascular diseases. However, the relationship between blood lipids and thyroid dysfunction is still controversial. This study aims to analyze the blood lipids in people with different thyroid functions.

METHODS

A total of 80937 adults were included in this population-based cross-sectional TIDE survey, which collected demographic and clinical data on thyroid function, blood lipid levels and other metabolic indicators. After screening, the final analysis included 10,747 participants, who were divided into hypothyroidism (n=311), subclinical hypothyroidism (n=5015), hyperthyroidism (n=203), subclinical hyperthyroidism (n=118) and control (n=5100) groups. The risk of dyslipidemia was analyzed by a logistic regression model and divided into groups of female menopausal.

RESULTS

After full adjustment, significant associations were found between hypothyroidism and hypertriglyceridemia. Subclinical hypothyroidism was associated with a significantly higher risk of hypertriglyceridemia and hyper-low density lipoprotein cholesterolemia. Hyperthyroidism was significantly correlated with a reduced risk of hypercholesterolemia and hyper-low density lipoprotein cholesterolemia but positively correlated with the risk of low-high density lipoprotein cholesterolemia. There was no significant association between subclinical hyperthyroidism and blood lipids. Hypothyroidism increased the risk of hypertriglyceridemia in both premenopausal and postmenopausal females. Subclinical hypothyroidism was significantly associated with increased hypertriglyceridemia and low-high density lipoprotein cholesterolemia in premenopausal females. Hyperthyroidism was significantly associated with a reduced risk of hypercholesterolemia and hyper-low density lipoprotein cholesterolemia in premenopausal females and an increased risk of low-high density lipoprotein cholesterolemia in postmenopausal female.

CONCLUSION

Abnormal thyroid function has an important effect on blood lipids and is closely related to female menopause.

The relationship between non-alcoholic fatty liver disease and hypothyroidism: A systematic review and meta-analysis

BACKGROUND

Whether hypothyroidism is related to non-alcoholic fatty liver disease (NAFLD) is controversial. Our aim was to investigate the relationship between NAFLD and hypothyroidism that may predict the NAFLD potential of these lesions and new prevention strategies in hypothyroidism patients.

METHODS

Totally 51,407 hypothyroidism patients with average 28.23% NAFLD were analyzed by Revman 5.3 and Stata 15.1 softwares in the present study. The PubMed and Embase databases were systematically searched for works published through May 9, 2020.

RESULTS

The blow variables were associated with an increased risk of NAFLD in hypothyroidism patients as following: increased of thyroid stimulating hormone (TSH) levels (odds ratio [OR] = 1.23, 1.07-1.39, P = .0001); old age (mean difference [MD] = 3.18, 1.57-4.78, P = .0001); increased of body mass index (BMI) (MD = 3.39, 2.79-3.99, P < .000001); decreased of free thyroxine 4 (FT4) levels (MD = -0.28, -0.53 to -0.03, P = .03). In addition, FT3 (MD = 0.11, -0.09-0.3, P = .29) had no association with the risk of NAFLD in hypothyroidism patients.

CONCLUSION

Our systematic review identified results are as following: hypothyroidism was positively associated with the risk of NAFLD. The increased concentration of TSH levels maybe a risk factor that increased incidence of NAFLD. The BMI of NAFLD patients was significantly higher than that of non-NAFLD patients. Old age was significantly associated with the incidence of NAFLD. FT4 was significantly associated with the risk of NAFLD due to its negatively effect while FT3 was not significantly related to the risk of NAFLD. Taken together, the present meta-analysis provides strong evidence that hypothyroidism may play a vital role in the progression and the development of NAFLD.

Environmentally relevant concentrations of carbamazepine induced lipid metabolism disorder of Chinese rare minnow (Gobiocypris rarus) in a gender-specific pattern

Carbamazepine (CBZ), an anticonvulsant and mood stabilizer, is ubiquitous distributed in aquatic environment. Though the toxicity and endocrine disrupting effect of CBZ on non-target organisms have been studied, its lipotoxity are scarcely known. To assess the lipotoxicity of CBZ, 2-month-old Chinese rare minnow were exposed to 0, 1, 10, and 100 μg/L CBZ for 90 d. Obvious dyslipidemia was observed after 30 d and 90 d exposure, whereas overt hyperlipidemia was observed in males at 100 μg/L treatments. Severe lipid droplet accumulation in livers was observed at 10 and 100 μg/L treatments for 30 d and in females, whereas those was observed at all treatments in males. In addition, serious mitochondria damage was observed in males at 100 μg/L treatments. After 90 d exposure, the enzyme activities of FAS and ACCα were significantly increased at 10 and 100 μg/L treatments, whereas HMGCR were markedly increased at 100 μg/L treatments (p < 0.05). However, ACCβ were markedly decreased in females at 10 and 100 μg/L treatments and in males at all treatments (p < 0.05). The transcription levels of fasn, accα, hmgcrα, fdft1, idi1, plin1, plin2, caveolin1, and caveolin2 were significantly increased at 100 μg/L treatments (p < 0.05). Moreover, the body weight was obviously increased at 10 and 100 μg/L treatments in males (p < 0.05). Our results confirmed that environmental relevant concentrations CBZ induced lipid metabolism disorder and mitochondria damage of Chinese rare minnow in a gender-specific pattern, which provided a new insight into the lipotoxicity mechanism of CBZ.

The Relationship Between Thyroid Function and Metabolic Syndrome and Its Components: A Cross-Sectional Study in a Chinese Population

OBJECTIVE

The present study examined the relationship between thyroid function status and the prevalence of metabolic syndrome in a Chinese population.

METHODS

Cross-sectional data were obtained from the Thyroid Disease, Iodine Nutrition and Diabetes Epidemiology (TIDE) Survey. A total of 62,408 subjects aged ≥18 years were enrolled. Differences in metabolic indicators and the prevalence of metabolic syndrome according to sex and thyroid function status were compared. Logistic regression was used to analyze the influence of thyroid function on metabolic syndrome and its components.

RESULTS

The prevalence of metabolic syndrome was generally higher in men than women. Overt hyperthyroidism and subclinical hypothyroidism had a significant effect on metabolism in men. Body mass index (BMI), waist circumference, and triglycerides (TGs) were significantly lower in men in the overt hyperthyroidism group, and BMI, waist circumference, systolic blood pressure (SBP) and TGs were higher in men in the subclinical hypothyroidism group than men in the normal group. Overt and subclinical hypothyroidism had significant impacts on metabolic components in women. BMI, waist circumference, TGs, SBP and DBP in the subclinical and overt hypothyroidism groups were significantly higher than the euthyroid group in women. The relative risk of abdominal obesity and hypertriglyceridemia was increased in women with hypothyroidism. Thyroid dysfunction had different effects on metabolic syndrome and its components before and after menopause.

CONCLUSION

Thyroid function had important effects on the prevalence of metabolic syndrome. Women with hypothyroidism, especially post-menopausal women, had a higher risk of metabolic syndrome than men.

Correlation Between Serum TSH Levels Within Normal Range and Serum Lipid Profile

The aim of the work was to investigate the correlation between serum TSH (thyrotropin) levels within normal range and serum lipids. A total of 1962 subjects with normal thyroid function were enrolled. The subjects were divided into four groups according to the quartiles of serum normal TSH levels, [Q₁ (0.27-1.68) mIU/l, Q₂ (1.69-2.35) mIU/l, Q₃ (2.36-3.07) mIU/l, and Q₄ (3.08-4.20) mIU/l]. The effect of serum normal TSH levels on serum lipid profiles of different age or gender was analyzed. The total cholesterol (TC), triglyceride (TG), and low-density lipoprotein cholesterol (LDL-C) levels of the Q₃ group and TG levels of the Q₄ group were higher than those of the Q₁ group in youth (p <0.05). The TC levels of the Q₃ group were higher than those of the Q₂ group in middle age (p <0.05). The LDL-C levels of middle age or elderly were higher than those of youth at the same TSH levels (p <0.05), while the TC levels of middle age were higher than those of youth in Q₁, Q₃, or Q₄ group (p <0.05), and the TC and HDL-C levels of elderly were higher than those of youth in the Q₂ group (p <0.05). The TG levels of the Q₃ group were higher than those of Q₁ group in males (p <0.05). The LDL-C levels of the Q₃ group were higher than those of the Q₁ group in females (p <0.05). In conclusion, the normal serum TSH levels were found to be closely related to serum lipid profiles, and with increasing TSH levels, serum lipids levels increased gradually.

Characterisation of the dynamic nature of lipids throughout the lifespan of genetically identical female and male Daphnia magna

Lipids play a significant role in regulation of health and disease. To enhance our understanding of the role of lipids in regulation of lifespan and healthspan additional studies are required. Here, UHPLC-MS/MS lipidomics was used to measure dynamic changes in lipid composition as a function of age and gender in genetically identical male and female Daphnia magna with different average lifespans. We demonstrate statistically significant age-related changes in triglycerides (TG), diglycerides (DG), phosphatidylcholine, phosphatidylethanolamine, ceramide and sphingomyelin lipid groups, for example, in males, 17.04% of TG lipid species decline with age whilst 37.86% increase in relative intensity with age. In females, 23.16% decrease and 25.31% increase in relative intensity with age. Most interestingly, the rate and direction of change can differ between genetically identical female and male Daphnia magna, which could be the cause and/or the consequence of the different average lifespans between the two genetically identical genders. This study provides a benchmark dataset to understand how lipids alter as a function of age in genetically identical female and male species with different average lifespan and ageing rate.

FABP4 levels in hypothyroidism and its relationship with subclinical atherosclerosis

Background/aim

The aim of this study is to evaluate the relationship between serum fatty acid binding protein 4 (FABP4) levels and carotid intima media thickness (CIMT) in patients with hypothyroidism.

Materials and methods

Forty subclinical hypothyroidism patients, 40 overt hypothyroidism patients, and 40 healthy controls were enrolled in the study. Blood pressure, body mass index, CIMT, fasting blood sugar, creatine, alanine aminotransferase, lipid parameters, insulin, free thyroxine, triiodothyronine, thyroid-stimulating hormone (TSH), thyroid peroxidase antibody (anti-TPO), thyroglobulin antibody (anti-TG), high-sensitivity C-reactive protein (Hs-CRP), and FABP4 levels of all participants were measured.

Results

Serum FABP4 levels were significantly higher in patients with subclinical and overt hypothyroidism than healthy controls (HCs) (P = 0.044 and P = 0.014, respectively). There was no significant difference in terms of FABP4 levels between patients with subclinical and overt hypothyroidism (P = 0.641). Serum TSH levels and serum FABP4 levels were positively correlated (r = 0.201, P = 0.039). CIMT was found to be higher in patients with subclinical and overt hypothyroidism than in HCs (P = 0.042 and P < 0.001, respectively). No correlation was found between CIMT and FABP4 levels (r = 0.038, P = 0.702). There was a positive correlation between CIMT and TSH, anti-TPO, anti-TG, triglycerides (TG), and total cholesterol levels. It was found that high TG levels were an independent factor that increased CIMT (r = 0.382, r2 = 0.146).

Conclusion

In patients with subclinical and overt hypothyroidism, the level of FABP4 increases and this increase is correlated with the increase in TSH level. It is thought that FABP4 does not play a role in atherosclerosis development in patients with hypothyroidism without metabolic disorder.

The Role of Thyroid Diseases and their Medications in Cardiovascular Disorders: A Review of the Literature

The association between thyroid disease and cardiovascular manifestations is significant and undeniable. Previous studies have explained several aspects of the effects of thyroid hormone on the heart and cardiovascular system. Accordingly, both hyper and hypothyroidism can cause important alterations in cardiac rhythm, output and contractility as well as vascular resistance and blood pressure. Since treating the thyroid abnormality, especially in its initial stages, could lead to a significant improvement in most of its resultant cardiovascular disturbances, early suspicion and recognition of thyroid dysfunction, is necessary in patients with cardiovascular manifestations. In this in-depth review, we discuss the physiological roles as well as the effects of abnormal levels of thyroid hormones on the cardiovascular system. We also review the effects of the medications used for the treatment of hyper and hypothyroidism on cardiac function. In the end, we discuss the association between thyroid function and amiodarone, an effective and frequently-used antiarrhythmic drug, because of its well-known effects on the thyroid.

Thyroid hormone therapy for subclinical hypothyroidism

Subclinical Hypothyroidism (SCH) is defined as a raised level of serum TSH level in the presence of normal circulating free thyroid hormones. SCH is a highly prevalent condition displaying some peculiarities, both in terms of the diagnostic and therapeutic approach, when specific population and/or concomitant diseases are taken into account. The debate upon whether LT4 therapy should be initiated or not in patients with SCH is a long lasting one and still it remains controversial. Current evidence supports the concept that the clinical consequences of SCH may be profoundly different in relation to several patient-specific characteristics. Aim of the present review is to provide updated indications for SCH treatment in specific clinical settings. These will include the management of SCH in obese and diabetic patients, in pregnant women, and in specific age groups. Treatment modalities, including LT4 doses and recommended follow-up strategy will also be discussed. In the era of "precision medicine" the decision to-treat-not-to-treat SCH should be individualized taking into account risks and beneficial outcomes of LT4 therapy. With this in mind, we reviewed the most relevant studies in the recent literature in order to provide evidence for or against LT4 replacement therapy for SCH in specific clinical settings.

Age-Related Resistance to Thyroid Hormone Action

The age-related resistance to thyroid hormones (THs) explains the paucity of symptoms and signs of hyperthyroidism in older adults and may partly explain the myriad of symptoms and signs of hypothyroidism in biochemically euthyroid older people. This review considers the available data on the mechanisms underlying TH resistance with aging and compares these physiologic changes with the changes observed in congenital TH resistance syndromes. Aging is associated with alterations in TH economy along with a host of changes in the responsiveness of various tissues to THs. The age-related resistance to THs can be attributed to decreased TH transport to tissues, decreased nuclear receptor occupancy, decreased activation of thyroxine to triiodothyronine, and alterations in TH responsive gene expression. Although an increase in serum TH levels is expected in syndromes of TH resistance, unchanged serum TH levels in the euthyroid elderly is the result of increased sensitivity to TH negative feedback with increased suppression of thyroid-stimulating hormone, decreased thyroidal sensitivity to thyroid-stimulating hormone, and decreased TH production and secretion. The current clinical evidence suggests that the age-related TH resistance is mostly an adaptive response of the aging organism. It is tempting to speculate that similar changes can occur prematurely in a group of younger people who present with signs and symptoms of hypothyroidism despite normal serum thyroid function tests.

Association between mild hyperthyrotropinemia and hypercholesterolemia in children with severe obesity

Background Severe obesity is associated with a number of cardiometabolic risk factors. Thyroid-stimulating hormone (TSH) levels are often slightly increased in children with obesity. The clinical significance of the mild elevation in TSH in children with obesity is unclear. Objective To examine the association between TSH and lipids in children with severe obesity. Methods We performed a retrospective analysis of records of children with severe obesity with simultaneous measurements of TSH and lipids. Children with TSH <0.3 mIU/L and ≥10 mIU/L were excluded. The relationship between TSH and lipids was evaluated using univariate/multiple variable linear and logistic regression. Results The study included 834 children (age 13.8 ± 4.1 years, males 46%, body mass index [BMI]: 36.9 ± 7.6 kg/m2; BMI z-score 2.6 ± 0.4). Seventy-four (8.9%) children had TSH between 5 and <10 mIU/L (high TSH [HTSH]). TSH was positively associated with non-high-density lipoprotein (HDL) cholesterol (β: 1.74; 95% confidence interval [CI] 0.29-3.20, p = 0.02). Total cholesterol and non-HDL cholesterol were higher in males with HTSH compared to those with normal TSH (175.5 vs. 163.5 mg/dL, p = 0.02 and 133.7 vs. 121.4 mg/dL, p = 0.02, respectively). The odds of elevated non-HDL cholesterol (≥145 mg/dL) was higher in males with HTSH relative to those with normal TSH (odds ratio [OR]: 2.78; 95% CI 1.35-5.69, p = 0.005). Conclusions TSH levels were positively associated with non-HDL cholesterol in children with severe obesity. Males with mildly elevated TSH had higher total cholesterol and non-HDL cholesterol compared to males with normal TSH. Further studies are warranted to determine if levothyroxine therapy would result in improvement in total cholesterol or non-HDL cholesterol in children with severe obesity with mildly elevated TSH.

Overt and Subclinical Hypothyroidism in the Elderly: When to Treat?

Hypothyroidism is characterized by increased thyrotropin (TSH) levels and reduced free thyroid hormone fractions while, subclinical hypothyroidism (sHT) by elevated serum TSH in the face of normal thyroid hormones. The high frequency of hypothyroidism among the general population in Western Countries made levothyroxine (LT4) one of the 10 most prescribed drugs. However, circulating TSH has been demonstrated to increase with aging, regardless the existence of an actual thyroid disease. Thus, when confronting an increase in circulating TSH levels in the elderly, especially in the oldest old, it is important to carry an appropriate diagnostic path, comprehensive of clinical picture as well as laboratory and imaging techniques. In the current review, we summarize the recommendations for a correct diagnostic workup and therapeutic approach to older people with elevated TSH value, with special attention to the presence of frailty, comorbidities, and poly-therapy. The treatment of choice for hypothyroid patients is hormone replacement with LT₄ but, it is important to consider multiple factors before commencing the therapy, from the age dependent TSH increase to the presence of an actual thyroid disease and comorbidities. When treatment is necessary, a tailored therapy should be chosen, considering poly-pharmacy and frailty. A careful follow-up and treatment re-assessment should be always considered to avoid the risk of over-treatment. It is important to stress the need of educating the patient for a correct administration of LT₄, particularly when poly-therapy is in place, and the importance of a tailored therapeutic approach and follow-up, to avoid overtreatment.

Hypothyroidism in the Elderly: Who Should Be Treated and How?

Hypothyroidism is among the most frequent chronic diseases in the elderly, and levothyroxine (l-T4) is worldwide within the 10 drugs more prescribed in the general population. Hypothyroidism is defined by increased serum thyroid-stimulating hormone (TSH) values and reduced circulating free thyroid hormones, whereas subclinical hypothyroidism (sHT) is characterized by free hormone fractions within the normal ranges and has been divided into two classes, depending on circulating TSH levels (above or below 10 mIU/L). Given that during aging, a natural trend toward higher values of circulating TSH has been reported, it is necessary to verify carefully the diagnosis of sHT to tailor an appropriate follow-up and ad hoc therapy, avoiding unnecessary or excessive treatment. In the current review, we evaluate the state of the art on hypothyroidism in the elderly with special focus on the effect of sHT on cognition and the cardiovascular system function. We also summarize the recommendations for a correct diagnostic workup and therapeutic approach to older people with an elevated TSH value, with special attention to the presence of frailty, comorbidities, and poly therapy. In conclusion, personalized therapy is crucial in good clinical practice, and in the management of older patients with sHT, multiple factors must be considered, including age-dependent TSH cutoffs, thyroid autoimmunity, the burden of comorbidities, and the possible presence of frailty. l-T4 is the drug of choice for the treatment of hypothyroid older people, but the risk of overtreatment, potential adverse drug reactions, and patient compliance should always be considered and thyroid status periodically reassessed.

Association Between Thyroid Dysfunction and Lipid Profiles Differs According to Age and Sex: Results from the Korean National Health and Nutrition Examination Survey

BACKGROUND

Lipid profiles of men and women change differently during the aging process. Guidelines recommend that dyslipidemia patients should consider screening for hypothyroidism without consideration of age or sex.

METHODS

Data from the sixth Korean National Health and Nutrition Examination Survey were used. A total of 4275 participants without thyroid disease and without a past history of dyslipidemia or dyslipidemia medication were evaluated. The association between thyroid dysfunction and lipid profiles (total cholesterol [TC], low-density lipoprotein cholesterol [LDLC], and triglycerides [TG]) was analyzed by age and sex.

RESULTS

The prevalence of thyroid dysfunction was significantly different according to TC and LDLC levels (p = 0.003 and p = 0.021, respectively). In women, the weighted prevalence of thyroid dysfunction was significantly different according to levels of TC, LDLC, and TG (p = 0.007, p = 0.016, and p = 0.044, respectively). However, in men, no association was found in any of the lipid profiles. Female participants were divided into two groups using a cutoff age of 55 years. In younger women, the weighted prevalence of thyroid dysfunction was different according to the levels of TC, LDLC, and TG (p = 0.013, p = 0.007, and p = 0.007, respectively). However, in older women, no association was found for any of the lipid profiles.

CONCLUSIONS

The prevalence of thyroid dysfunction was significantly different according to lipid profiles, and this association differed by age and sex.

[Hypothyroidism-when and how to treat?]

The diagnosis of hypothyroidism is primarily based on clinical signs and symptoms as well as measurement of thyroid-stimulating hormone (TSH) concentration. Subclinical hypothyroidism is characterized by elevated TSH with normal serum free thyroxine (fT₄) and triiodothyronine (fT₃) levels, while in manifest hypothyroidism serum fT₄ and fT₃ levels are reduced. Common causes of primary hypothyroidism are autoimmune thyroiditis as well as therapeutic interventions, such as thyroid surgery or radioiodine therapy. Signs and symptoms of hypothyroidism include fatigue, bradycardia, constipation and cold intolerance. In subclinical hypothyroidism, symptoms may be absent. Initiation of levothyroxine (T₄) therapy not only depends on the level of TSH elevation, but also on other factors, such as patient age, presence of pregnancy or comorbidities. Treatment of patients with subclinical hypothyroidism is still a controversial topic. In general, thyroid hormone replacement therapy in non-pregnant adults ≤ 70 years is clearly indicated if the TSH concentration is >10 mU/l. Standard of care for treatment of hypothyroidism is T₄ monotherapy. The biochemical treatment goal for T₄ replacement in primary hypothyroidism is a TSH level within the reference range (0.4-4.0 mU/l). In contrast, in secondary hypothyroidism, serum fT₄ levels are the basis for adjusting thyroid hormone dosage. Inadequate replacement of T₄ resulting in subclinical or even manifest hyperthyroidism should urgently be avoided. T₄/liothyronine (T3) combination therapy is still a matter of debate and not recommended as standard therapy, but may be considered in patients with persistence of symptoms, despite optimal T₄ treatment, based on expert opinion.

Comprehensive Metabolic Profiling Reveals a Lipid-Rich Fingerprint of Free Thyroxine Far Beyond Classic Parameters

OBJECTIVE

Thyroid hormones are ubiquitously involved in human metabolism. However, the precise molecular patterns associated with alterations in thyroid hormones levels remain to be explored in detail. A number of recent studies took great advantage of metabolomics profiling to outline the metabolic actions of thyroid hormones in humans.

METHODS

Among 952 participants in the Study of Health in Pomerania, data on serum free thyroxine (FT4) and thyrotropin and comprehensive nontargeted metabolomics data from plasma and urine samples were available. Linear regression analyses were performed to assess the association between FT4 or thyrotropin and metabolite levels.

RESULTS AND CONCLUSION

After accounting for major confounders, 106 of 613 plasma metabolites were significantly associated with FT4. The associations in urine were minor (12 of 587). Most of the plasma metabolites consisted of lipid species, and subsequent analysis of highly resolved lipoprotein subclasses measured by proton nuclear magnetic resonance spectroscopy revealed a consistent decrease in several of these species (e.g., phospholipids) and large low-density lipoprotein and small high-density lipoprotein particles. The latter was unique to men. Several polyunsaturated and saturated fatty acids displayed an association with FT4 in women only. A random forest-based variable selection approach using phenotypic characteristics revealed higher alcohol intake in men and an adverse thyroid state and menopause in women as the putative mediating factors. In general, our observations have confirmed the lipolytic and lipogenic effect of thyroid hormones even in the physiological range and revealed different phenotypic characteristics (e.g., lifestyle differences) as possible confounders for sex-specific findings.

A Renewed Focus on the Association Between Thyroid Hormones and Lipid Metabolism

Thyroid dysfunction, manifesting as either overt or subclinical hypothyroidism, negatively affects lipid metabolism: this leads to hypercholesterolemia which progressively increases the risk for cardiovascular disease and, potentially, mortality. Hypercholesterolemia in hypothyroidism is mainly due to a reduction in low-density lipoprotein (LDL) receptor activity, this accompanied by concomitant diminishing control by triiodothyronine (T3) of sterol regulatory element-binding protein 2 (SREBP-2), which modulates cholesterol biosynthesis by regulating rate-limit degrading enzyme 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA) activity. Recently, 3,5-diiodothyronine (T2), a natural thyroid hormone derivative, was found to repress the transcription factor carbohydrate-response element-binding protein (ChREBP) and also to be involved in lipid catabolism and lipogenesis, though via a different pathway than that of T3. While thyroid hormone could therapeutically reverse the dyslipidemic profile commonly occurring in hypothyroidism, it should be borne in mind that the potency of the effects may be age-and sex-dependent. Thyroid hormone administration possibly also sustains and enhances the efficacy of hypolipidemic drugs, such as statins, ezetimibe and proprotein convertase subtilisin/kexin type 9 (PCSK9), in patients with dyslipidemia and hypothyroidism.

Dyslipidemia in subclinical hypothyroidism requires assessment of small dense low density lipoprotein cholesterol (sdLDL-C)

BACKGROUND

Usually both hypothyroidism and hyperthyroidism are related to the cardiovascular and cerebrovascular disease development. The relationship between subclinical hypothyroidism has been widely investigated but the findings remain controversial. The aim of the present study was to evaluate the lipid profile in patients with subclinical hypothyroidism (SHypo) in comparison to controls and to determine the association of SHypo and dyslipidemia in attempt to find importance of small dense low-density lipoprotein cholesterol (sdLDL-C) in atherosclerosis.

MATERIAL AND METHODS

In this study we included 100 women, aged 30 to 70 years that were divided into subgroups according to their age. According to the values of levels of thyroid hormones they were divided into euthyroid (control) group (n = 64) and (newly discovered) subclinical hypothyroidism (SHypo) group (n = 36). A high-sensitivity C-reactive protein (hs-CRP) and lipid profile, including small dense low-density lipoprotein cholesterol (sdLDL-C) were determined. Body weight and height were measured and BMI calculated. History of the current illness, medication, alcohol consumption and cigarettes smoking were noted.

RESULTS

Changed lipid profile as well as elevated triglycerides and sdLDL-C were observed in the group with subclinical hypothyroidism compared to the control group.

CONCLUSIONS

It is important to determine serum lipid levels, especially serum sdLDL-C levels at an early stage of subclinical hypothyroidism, since they represent atherogenic LDL particles and are better indicators for dyslipidaemia in subclinical hypothyroidism and the development of atherosclerosis with potential complications such as cardiovascular and cerebrovascular diseases.

Subclinical hypothyroidism, lipid metabolism and cardiovascular disease

Subclinical hypothyroidism is defined by elevated serum thyrotropin in presence of normal free thyroid hormones. Lipid metabolism is influenced by thyroid hormone and many reports showed that lipids status worsen along with TSH level. Subclinical hypothyroidism has been also linked to other cardiovascular risk factors such as alteration in blood pressure and increased atherosclerosis. Further evidences suggested that mild dysfunction of thyroid gland is associated with metabolic syndrome and heart failure. Thyrotropin level seems the best predictor of cardiovascular disease, in particular when its levels are above 10mU/L. However, despite these observations, there is no clear evidence that levothyroxine therapy in subjects with milder form of subclinical hypothyroidism could improve lipid status and the other cardiovascular risk factors. In this review, we address the effect of thyroid hormone and cardiovascular risk, with a focus on lipid metabolism.

Gender impact on the correlation between thyroid function and serum lipids in patients with differentiated thyroid cancer

The present study aimed to explore the association between thyroid stimulating hormone (TSH) and serum lipids in patients with differentiated thyroid cancer (DTC), with a focus on the risk of hyperlipidemia between different genders. The study included 352 DTC patients who were ready to receive I-131 therapy as well as 352 matched normal controls. In the DTC group, 157 patients were monitored for TSH and lipid parameters prior to and after 1 month of thyroxine therapy. Results were analyzed using t-tests, Pearson bivariate correlation and binary logistic regression analyses. All participants were divided into 3 subgroups according to TSH levels: Subgroup 1 (normal TSH level), subgroup 2 (TSH between 5 and 30 µIU/ml), and subgroup 3 (TSH >30 µIU/ml). Serum total cholesterol (TC), triglycerides (TG), and low-density lipoprotein-cholesterol (LDL-C) levels were significantly higher in the DTC group than in the control group. The levels of these parameters decreased after thyroxine therapy and significant positive correlations were observed between TSH and TC, and TG and LDL-C in both genders. Binary logistic regression demonstrated that female DTC patients had higher risks of developing hyperlipidemia than male patients, and these risks increased when TSH increased. For example, the odds ratios (ORs) of high TC in subgroup 2 were 3.30 in males and 4.60 in females, respectively. However, in subgroup 3, the ORs were 9.40 in males and 13.12 in females, respectively. The results of the present study showed that after thyroidectomy, the risk of dyslipidemia markedly increased in DTC patients. More importantly, female patients had a higher risk than male patients.

Gender and Age Impacts on the Association Between Thyroid Function and Metabolic Syndrome in Chinese

The relationship between thyroid dysfunction and metabolic syndrome (MS) is complex. We aimed to explore the impact of gender and age on their association in a large Chinese cohort. This cross-sectional study enrolled 13,855 participants (8532 male, 5323 female), who self-reported as healthy without any known previous diseases. Clinical data including anthropometric measurements, thyroid function, and serum metabolic parameters were collected. The associations between thyroid function and MS of both genders were analyzed separately after dividing thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), and age into subgroups. MS risks were calculated by binary logistic regression models. Young males had significantly higher MS prevalence than females, yet after menopause, females had higher prevalence than males. Females had higher incidence of thyroid dysfunction than males. By using TSH quartiles as the categorical variables and the lowest quartile as reference, significantly increased MS risk was demonstrated in quartile 4 for males, yet quartiles 3 and 4 for females. By using FT3 quartiles as the categorical variables, significantly increased MS risk was demonstrated in quartile 2 to 4 for females only. By using age subgroups as the categorical variables, significantly increased MS risk was shown in both genders, with females (4.408-58.455) higher than males (2.588-4.943). Gender and age had substantial influence on thyroid function and MS. Females with high TSH and high FT3 had higher MS risks than males. Aging was a risk for MS, especially for females. Urgent need is necessary to initiate interventional programs.

Gender and Age Impact on the Association Between Thyroid-Stimulating Hormone and Serum Lipids

The relationship between thyroid-stimulating hormone (TSH) and hyperlipidemia is still a topic of debate. We aimed to explore the impact of gender and age on the association between serum TSH and lipid profile in a large cohort of Chinese.This cross-sectional study enrolled 13,915 participants (8565 male, 5350 female), who self-reported as healthy without any known previous diseases. Clinical data including anthropometric measurements, thyroid function, and other serum parameters were collected. The associations between TSH and hyperlipidemia of males and females were analyzed separately after dividing TSH and age into subgroups. Odds ratio for hyperlipidemia was calculated by binary logistic regression models.Young males had significantly higher prevalence of hypercholesterolemia, hypertriglyceridemia, and high serum low-density lipoprotein-cholesterol than females, yet after menopause, females had higher prevalence than males. TSH was positively associated with hyperlipidemia independent of thyroid hormones. Males showed more reduced risks of hyperlipidemia in low TSH concentrations, while females demonstrated more enhanced risks of hyperlipidemia in high TSH concentrations. For instance, if TSH was lower than 0.3 μIU/mL, the risks of developing hypercholesterolemia and hypertriglyceridemia in males were only 0.198 (P < 0.01) and 0.425 (P < 0.05) of the reference TSH risks (between 2.0 and 3.0 μIU/mL), while in females the risks were 0.553 (P < 0.05) and 0.642 (P > 0.05), respectively. If TSH was higher than 4.0 μIU/mL, women displayed significantly higher risks of developing hypertriglyceridemia than the reference TSH risks (P < 0.05), yet, men did not demonstrate such significances.Our results showed thyroid hormone independent positive associations between serum TSH and lipids, which were substantially influenced by gender and age. Males demonstrated more protective effects of low TSH against hyperlipidemia, while females showed more detrimental effects of high TSH on hyperlipidemia.

Effectiveness of early identification and electronic interventions for teens with risk factors for the development of heart disease and diabetes

PURPOSE

Serum risk factors for the development of heart disease and diabetes are not routinely evaluated in teens. The intent of this study was to determine the prevalence of these risk factors in teens and evaluate the effectiveness of a two-part electronic education program (recurring electronic lifestyle education program [REEP]) on reducing risks.

DATA SOURCES

Teens (n = 170) were recruited from one urban and one rural high school in the mid-Atlantic in 2014. Following baseline data collection in February, REEP was initiated and data collection repeated at 12 weeks. Data were analyzed and students sent a report with results and recommendations.

CONCLUSIONS

One or more serum and/or physical risk factors were found in the majority of students with low vitamin D and elevated body mass index (BMI) being the most common. Correlations existed between elevated BMI and elevated diastolic blood pressure, low vitamin D, and low high-density lipoprotein. All but one risk factor (BMI) improved at 12 weeks.

IMPLICATIONS FOR PRACTICE

The majority of teens had one or more physical and/or serum risk factors. Using multiple electronic methods to deliver healthy lifestyle recommendations helps lower these risks. Also, Blackboard, an electronic learning platform, was found to be an effective data management and communication center.

Neonatal hyperthyroidism on rat heart: interrelation with nitric oxide and sex

PURPOSE

To clarify the mechanism mediating the effect of hyperthyroidism on cardiac function during the second month of life in rats.

METHODS

Male and female Sprague-Dawley rats were assigned to a control or to a triiodothyronine (T3)-treated group. Treatment of each group was started on the third day after birth. Control rats (Eut) received 0.9 NaCl [0.1 ml/100 g body weight (BW)] every second day during 60 days and T3-treated rats (Hyper) received subcutaneous (SC) T3 injections every second day during 60 days.

RESULTS

Hyperthyroidism decreased left ventricle volume only in male rats. Female euthyroid rats presented higher atrial nitric oxide synthase (NOS) activity than male rats and hormonal treatment decreased this enzyme's activity in both sexes. Euthyroid male and female rats had similar atrial NOS protein levels, but females had higher caveolin (cav) 3 protein levels. T3 treatment increased this protein only in males. Female rats had lower ventricular NOS activity than male rats; hyperthyroidism increased NOS activity in both sexes but this effect was associated with lower cav 3 protein levels. Hyperthyroidism did not change cav 1 protein levels in both male and female rats.

CONCLUSIONS

The results of this study demonstrating clinically relevant sex-related differences in the pathophysiology of the hyperthyroid heart have raised new questions regarding the mechanisms responsible for the observed differences. This study suggests that sex-related intrinsic factors such as nitric oxide may modulate the response to hyperthyroidism that leads to cardiovascular dysfunction.

Subclinical hypothyroidism might worsen the effects of aging on serum lipid profiles: a population-based case-control study

BACKGROUND

Dyslipidemia is an important global health problem, particularly in the elderly population. Traditionally, the high prevalence of dyslipidemia in elderly people is considered a "natural condition." Notably, subclinical hypothyroidism (SCH) is one of the most important risk factors for dyslipidemia. Few studies have assessed whether SCH plays a role in the increase in age-related dyslipidemia. This study aimed to explore the association between SCH and lipid profiles in different age groups.

METHODS

This was a large-scale, population-based, case-control study. The population was derived from the REACTION study conducted across China. A total of 17,046 individuals (8827 cases and 8219 controls) aged 40 years or older were enrolled in the final analyses. The relationships between SCH and serum lipid parameters in each age group were evaluated after adjustment for thyroid hormones and common confounding factors.

RESULTS

In the entire population, thyrotropin (TSH), the key indicator of SCH, was positively associated with cholesterol parameters (total cholesterol [TC] and low-density lipoprotein cholesterol [LDL-C]) through the sixth decade of life. After adjusting for common confounding factors and thyroid hormones, each 1 mIU/L increase in TSH was estimated to elevate the TC level by 0.0147 mmol/L and 0.0551 mmol/L, respectively, in individuals aged 40-49 years and 60-69 years. Similarly, with each 1 mIU/L increase in TSH, the LDL-C level tended to show gradually greater increases as age increased. In moderately old subjects (60-69 years), mild (TSH≤10 mIU/L) and significant (TSH>10 mIU/L) SCH increased the concentration of TC approximately 1.03- and 1.36-fold, and the concentration of LDL-C approximately 1.19- and 1.65-fold, respectively, when compared with younger subjects.

CONCLUSIONS

TSH exhibited a stronger effect on the TC and LDL-C level in moderately old subjects than in younger subjects. SCH might augment and worsen the effects of aging on serum lipid profiles.

Normal thyroid-stimulating hormone levels, autoimmune activation, and coronary heart disease risk

Whether euthyroid status affects cardiovascular disease risk is unclear. We aimed to investigate whether serum thyroid-stimulating hormone (TSH) levels within the normal range are related to the risk of coronary heart disease (CHD). In participants of the Turkish Adult Risk Factor Study (mean age 52.7±11.5), in whom TSH was measured in the 2004/05 survey, cross-sectional and longitudinal analyses were performed. Subjects with TSH concentrations<0.3 and >4.2 mIU/L were excluded to ensure euthyroid status leaving 956 individuals as the study sample. Mean follow-up was 4.81±1.3 years. Men had 18% lower (p<0.001) geometric mean TSH levels (1.10 mIU/L) than women (1.35 mIU/L). Correlations of TSH with risk variables were notably virtually absent except weakly positive ones in men with age and systolic blood pressure (SBP). The age-adjusted TSH mid-tertile in men was associated with lowest lipoprotein [Lp](a), apoB, and total cholesterol values. Incident CHD was predicted in Cox regression analyses in men [HR of 2.45 (95 %CI 1.05; 5.74] and in combined sexes by the lowest compared with the highest TSH tertile, after adjustment for age, smoking status, SBP, and LDL-cholesterol. Analysis for combined prevalent and incident CHD stratified by metabolic syndrome (MetS) confirmed the independent association with the lowest TSH tertile in men, specifically in men without MetS. TSH levels within normal range, low due to partial assay failure, may manifest as independent predictors of incident CHD, particularly in middle-aged men. Autoimmune responses involving serum Lp(a) under oxidative stress might be implicated mechanistically.

Thyroid Function, Prevalent Coronary Heart Disease, and Severity of Coronary Atherosclerosis in Patients Undergoing Coronary Angiography

This study investigated if free T4 and TSH concentrations or thyroid function categories were associated with prevalent CHD and the severity of coronary atherosclerosis in a population undergoing coronary angiography. This was a cross-sectional study including 1799 patients who were consecutively admitted and underwent coronary angiography. We evaluated the severity of coronary atherosclerosis using Gensini score. In the entire study population, free T4 level was inversely associated with prevalent CHD (OR = 0.95, 95% CI 0.91-0.99, P = 0.01) and the natural log-transformed Gensini score (ln(Gensini score)) (β = -0.03, 95% CI -0.05--0.01, P = 0.005). The odds of CHD increased gradually across hyperthyroidism, subclinical hypothyroidism, and overt hypothyroidism groups using the euthyroid group as the reference, and the trend is borderline significant (P for trend = 0.051). When comparing to the euthyroid group, ln(Gensini score) of the overt hypothyroidism group was significantly higher (P = 0.009), but the trend was not significant (P for trend = 0.08). A significant association of thyroid function with CHD or ln(Gensini score) in euthyroid patients was not observed. The present study demonstrated an association of thyroid function with prevalent CHD and the severity of coronary atherosclerosis in a population undergoing coronary angiography. However, this association was not observed in euthyroid individuals.

Association of thyroid-stimulating hormone and cardiovascular risk factors

Thyroid hormone plays an important role in regulating the lipid and glucose metabolism. Previously, much attention has been drawn to define the pathophysiological relationship between thyroid dysfunction and the incidence of cardiovascular diseases (CVDs). While the conditions of overt hypothyroidism and subclinical hypothyroidism were both emphasized, the association between CVD risks and the deregulated circulating thyroid-stimulating hormone (TSH) level remains to be elucidated. Nevertheless, multiple TSH-mediated physiological adaptations, including alteration of the serum lipids, body mass index, blood pressure and insulin sensitivity, have led to the difficulty of clearly examining the association between the TSH level and CVD prevalence. The current review aims to 1) summarize the evidence for the role of thyroid dysfunction and TSH abnormality in CVD pathogenesis and 2) explore the possible underlying molecular mechanisms of TSH-mediated cardiovascular pathology in hopes of providing better therapeutic strategies for the patients with deregulated TSH.

Serum cholesterol and triglyceride concentrations in diabetic patients with subclinical hypothyroidism

OBJECTIVE

To assess whether subclinical hypothyroidism is associated to elevations in serum cholesterol and triglyceride levels in patients with type 2 diabetes.

PATIENTS AND METHODS

From a total population of 1,112 patients with type 2 diabetes screened for thyroid dysfunction (thyrotropin measurement), a group of 325 patients with normal thyroid function and another group of 29 patients with subclinical hypothyroidism were selected. No patient had known dyslipidemia or was taking lipid lowering medication.

RESULTS

Patients with subclinical hypothyroidism had serum levels of total cholesterol (4.88 ± 0.74 mmol/L), HDL cholesterol (1.37 ± 0.34 mmol/L), LDL cholesterol (2.94 ± 0.58 mmol/L), and triglycerides (1.05 [0.88-1.41] mmol/L) that did not significantly differ from those found in euthyroid patients (4.79 ± 0.83, 1.33 ± 0.36, 2.87 ± 0.76, and 1.11 [0.81-1.43] mmol/L, respectively). Multiple regression analysis showed no association between TSH and serum lipid levels.

CONCLUSION

These results suggest that, in our population, there are no significant differences in serum cholesterol and triglyceride levels between diabetic patients with normal and reduced thyroid function.

Relationship between thyroid hormones, resting energy expenditure and cardiometabolic risk factors in euthyroid subjects

BACKGROUND & AIMS

Whereas hypothyroid subjects have a decreased resting energy expenditure (REE), it is unknown whether REE is associated with TSH in euthyroid subjects. It is also uncertain whether there is an association between cardiometabolic risk factors and TSH among euthyroid subjects. The primary aim was to test whether REE and TSH are associated in euthyroid subjects. The second aim was to evaluate the association between TSH and cholesterol, HDL-cholesterol, triglycerides, glucose and blood pressure.

METHODS

885 Caucasian euthyroid subjects (75% women) aged 18-79 years and with a median body mass index of 28.6 kg/m(2) were consecutively studied at our Research Center. REE was measured using a canopy-equipped indirect calorimeter. Multivariable regression of 25(th), 50(th) and 75(th) percentiles was used to evaluate the association between the outcomes (REE, cholesterol, HDL-cholesterol, triglycerides, glucose and blood pressure) and the predictors (TSH, FT4 and FT3) controlling by gender, age and body mass index.

RESULTS

REE was not associated with TSH, FT4 and FT3 at any percentile. On the contrary, a positive association between TSH and triglycerides was evident at all percentiles. A positive association between FT3 and HDL-cholesterol was also present but only at the 75(th) percentile.

CONCLUSIONS

REE is not associated with TSH in euthyroid subjects. It is however positively associated with triglycerides confirming the findings of recent population studies.

Sex-specific associations between thyrotropin and serum lipid profiles

BACKGROUND

Population-based studies investigating the sex-specific association between thyrotropin (TSH) levels and serum lipid concentrations are scarce. We examined the association between TSH and total cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, and triglycerides in men and women from the general population. Furthermore, the association with TSH outside and within the reference range and lipid levels was studied.

METHODS

Individual data of 13,571 men and women without lipid medication of four population-based studies conducted in Western European adults were pooled for cross-sectional analyses. The association between TSH levels and lipid concentrations were analyzed by calculating sex-specific multivariable median regression models.

RESULTS

In the pooled population, serum TSH levels were significantly positively associated with triglyceride values in men and with total cholesterol, LDL cholesterol, and triglyceride values in women. In the pooled male population, low serum TSH levels (<3.0 mIU/L) were significantly associated with lower total cholesterol, while high serum TSH levels (≥ 3.0 mIU/L) were associated with higher triglyceride values. In the pooled female population, low serum TSH levels were significantly associated with lower total cholesterol, LDL cholesterol, and HDL cholesterol. High TSH levels were associated with higher total cholesterol and LDL cholesterol in the pooled female population. In both sexes, serum TSH levels within the reference range (0.3-3.0 mIU/L) were significantly positively associated with triglyceride concentrations.

CONCLUSIONS

Increasing levels of TSH were associated with a less favorable lipid profile in both men and women from the general population. In both sexes, TSH levels within the reference range were significantly positively associated with triglyceride concentrations.

Body Mass Index Is Associated with Hypercholesterolemia following Thyroid Hormone Withdrawal in Thyroidectomized Patients

Thyroid hormone withdrawal (THW) for postoperative radioiodine adjuvant therapy or diagnostic radioiodine whole body scan in patients with differentiated thyroid cancers results in acute thyroid hormone deficiency and abnormal lipid profiles. To better clarify the clinical pattern of dyslipidemia occurring after THW, we retrospectively analyzed the association between serum total cholesterol level after THW and various clinical factors in a total of 61 patients who underwent total thyroidectomy due to papillary thyroid cancers from January 2010 to March 2012, in Severance Hospital, Seoul, Korea. Preoperative baseline total cholesterol was significantly correlated with post-THW total cholesterol level; however, age, gender, or elevated TSH level after THW itself was not correlated with post-THW total cholesterol level. A significant correlation between preoperative measured BMI and post-THW total cholesterol level was found (r = 0.263, P = 0.041). In multiple logistic analysis, BMI was an independent determining factor of post-THW total cholesterol level (P = 0.012).

2013 ETA Guideline: Management of Subclinical Hypothyroidism

Subclinical hypothyroidism (SCH) should be considered in two categories according to the elevation in serum thyroid-stimulating hormone (TSH) level: mildly increased TSH levels (4.0-10.0 mU/l) and more severely increased TSH value (>10 mU/l). An initially raised serum TSH, with FT4 within reference range, should be investigated with a repeat measurement of both serum TSH and FT4, along with thyroid peroxidase antibodies, preferably after a 2- to 3-month interval. Even in the absence of symptoms, replacement therapy with L-thyroxine is recommended for younger patients (<65-70 years) with serum TSH >10 mU/l. In younger SCH patients (serum TSH <10 mU/l) with symptoms suggestive of hypothyroidism, a trial of L-thyroxine replacement therapy should be considered. For such patients who have been started on L-thyroxine for symptoms attributed to SCH, response to treatment should be reviewed 3 or 4 months after a serum TSH within reference range is reached. If there is no improvement in symptoms, L-thyroxine therapy should generally be stopped. Age-specific local reference ranges for serum TSH should be considered in order to establish a diagnosis of SCH in older people. The oldest old subjects (>80-85 years) with elevated serum TSH ≤10 mU/l should be carefully followed with a wait-and-see strategy, generally avoiding hormonal treatment. If the decision is to treat SCH, then oral L-thyroxine, administered daily, is the treatment of choice. The serum TSH should be re-checked 2 months after starting L-thyroxine therapy, and dosage adjustments made accordingly. The aim for most adults should be to reach a stable serum TSH in the lower half of the reference range (0.4-2.5 mU/l). Once patients with SCH are commenced on L-thyroxine treatment, then serum TSH should be monitored at least annually thereafter.

Subclinical hypothyroidism and indices for metabolic syndrome in Japanese women: one-year follow-up study

CONTEXT

Subclinical hypothyroidism (SCH) and metabolic syndrome (MetS) increase with age; however, their relationship remains unclear.

OBJECTIVE

Our objective was to investigate the relationship between SCH and indices of metabolic syndrome and follow up subjects for 1 year.

DESIGN

Cross-sectional and longitudinal follow-up studies of cases were collected from Takasaki Hidaka Hospital between 2003 and 2007.

PARTICIPANTS

Overall, 11 498 participants of health checkups were analyzed. The mean age was 48 ± 9 years.

MAIN OUTCOME MEASURES

The relationship between SCH and indices of MetS were examined.

RESULTS

Serum free T4 levels were lower in women than men in most of the age groups, and the prevalence of SCH, 6.3% in women vs 3.4% in men, increased with age, reaching 14.6% in 70-year-old women. Multivariate logistic-regression analyses revealed that waist circumference and the serum triglyceride and low-density lipoprotein-cholesterol levels were significantly higher in subjects with SCH than without among women. Reflecting these findings, the adjusted odds ratio of MetS in patients with SCH was higher than in the euthyroid subjects in women with an odds ratio of 2.7 (95% confidence interval 1.1-5.6; P = .017) but not in men. Furthermore, progression from euthyroid into SCH resulted in a significant increase in the serum triglyceride levels but not low-density lipoprotein-cholesterol in women.

CONCLUSION

Japanese women exhibited a high prevalence of SCH associated with low free T4 levels. There was a strong association between SCH and several indices of metabolic syndrome in women. SCH may affect serum triglyceride levels and be a risk factor for metabolic syndrome.

Is subclinical hypothyroidism a cardiovascular risk factor in the elderly?

CONTEXT

The negative impact of subclinical hypothyroidism (sHT) on cardiovascular risk, widely recognized in young adults (aged <55-60 y), is still debated in the elderly (>65 y), especially in the oldest olds (>80 y).

EVIDENCE ACQUISITION

We searched Medline for reports published with the following search terms: "hypothyroidism," "subclinical hypothyroidism," "ageing," "elderly," "L-thyroxin," "thyroid," "guidelines," "treatment," "quality of life," "cardiovascular risk," "heart failure," "coronary heart disease" (CHD), "atherosclerosis," and "endothelial dysfunction." We limited our search to reports in English published after 1980, although we incorporated some reports published before 1980. We supplemented the search with records from personal files, textbooks, and relevant articles. Analyzed parameters included the epidemiology of thyroid failure, the effect of thyroid hormone on the aging process, cardiovascular function, and CHD risk factors. We also included the potential benefits of L-T4 therapy on the quality of life, cardiovascular events, and survival.

EVIDENCE SYNTHESIS

TSH levels increase with age, even in older people without thyroid disease. Most longitudinal studies show an increased risk for CHD events and mortality in sHT participants. This increase is less evident in the elderly, mainly in cases of serum TSH values above 10 mIU/L. Lower mortality rate in a cohort of the oldest olds (>85 y) has been reported.

CONCLUSIONS

sHT in older people should be not regarded as a unique condition, and moderately old patients (aged <70-75 y) could be considered clinically similar to the adult population, albeit with a higher optimal TSH target value. Conversely, the oldest old subjects should be carefully followed with a wait-and-see strategy, generally avoiding hormonal treatment. The decision to treat elderly people is still an unresolved clinical challenge--first, due to a lack of appropriately powered randomized controlled trials of L-T4 in sHT patients, examining cardiovascular hard endpoints in various classes of age; and second, because of the negative effects of possible overtreatment.

Thyroid dysfunction in the elderly

Thyroid dysfunction is common in the general population, and mild or subclinical forms can be present in more than 10% of individuals aged >80 years. The diagnosis of abnormal thyroid hormone concentrations in people aged >60 years poses a challenge, as the clinical presentation of thyroid dysfunction is usually nonspecific, and ageing is associated with a number of physiological changes that can affect thyroid function test results. Furthermore, the presence of acute or chronic nonthyroidal illnesses and the use of medications that interfere with thyroid function tests are common confounders in the determination of thyroid status in the elderly. Early diagnosis and treatment of overt thyroid dysfunction is crucial in this population in view of the marked effects of abnormal circulating thyroid hormone levels on a number of organ systems, including the heart, the skeleton and the neurological system. The clinical significance of mild thyroid overactivity and underactivity remains uncertain, and the need for treatment of subclinical thyroid dysfunction is much debated. A number of large epidemiological studies have identified associations between mild thyroid dysfunction and short-term as well as long-term adverse outcomes, and a small but increasing number of randomized controlled intervention studies have been reported. Guidelines recommend treatment of thyroid dysfunction on the basis of the degree of abnormal serum TSH concentrations, patient age and associated comorbidities. This Review describes the current evidence on the prevalence, diagnosis, management and long-term consequences of thyroid dysfunction in the elderly.