Subclinical hypothyroidism and cardiovascular risk: recommendations for treatment

The definition of subclinical hypothyroidism (SCH) is solely biochemical: a serum free T4 level within the reference range in the presence of an elevated serum thyroid-stimulating hormone (TSH) level. While overt hypothyroidism is associated with an increased cardiovascular disease risk, SCH, the mildest form of hypothyroidism, may also be associated with an increased cardiovascular disease risk, but to a lesser degree. Recent evidence points to a significant trend toward an increase in cardiovascular risk at higher TSH levels, with TSH levels ≥10 mIU/L associated with increased cardiovascular morbidity and mortality. It is generally recommended to treat with thyroid hormone those individuals with SCH and TSH values ≥10 mIU/L. Treatment of patients with SCH and TSH values <10 is controversial but may be considered in selected patients.     

Subclinical hypothyroidism in Addison's disease.

Fourteen patients with Idiopathic Addison's disease (IAD) were studied in order to detect a possible subclinical hypothyroid state. All were clinically euthyroid with normal serum thyroxine (T4) and serum 3,5',5'-triiodothyronine (T3). Eleven had circulating thyroid microsomal antibodies in blood. The mean basal serum TSH was significantly higher than that of the control group but only three patients had values above the upper normal range. The mean value of serum T4 was decreased as compared to that of the normal persons, while serum 3,3',5'-triiodothyronine was elevated. 7.5 mU bovine thyrotrophin per kilogram body weight injected intravenously caused a rise in serum T3 not different from the response in normals. However, as well increasing serum TSH as increasing microsomal antibody titer correlated significantly to decreasing thyroidal release of T3. Our results suggest that clinically euthyroid patients suffering from IAD might have a beginning thyroidal insufficiency because of a progressive immunological damage of the thyroid.     

Subclinical thyroid disease: subclinical hypothyroidism and hyperthyroidism

Subclinical hypothyroidism (SHT) and subclinical hyperthyroidism (SCH) are defined as normal serum free T4 and T3 levels associated with elevated (SHT) or subnormal (SCH) serum TSH levels, respectively. Symptoms and signs of thyroid dysfunction are scarce. The prevalence is low. In SHT, total cholesterol and LDL-C are modestly elevated and levothyroxine may influence the lipids levels. There is decreased cardiac contractility and increased peripheral vascular resistance that improve with treatment. SCH is associated with atrial fibrillation, increased cardiac contractility and left ventricular mass, diastolic and systolic dysfunction that can be reversed with beta-adrenergic antagonists. Bone density is reduced in SCH. Depression, panic disorders and alterations in cognitive testing are frequent in SHT. Treatment of SHT is recommended for serum TSH levels greater than 8 mU/L and presence of thyroid antibodies. Endogenous SCH should be treated for serum TSH levels less than 0.1 mU/L, in the presence of symptoms and in elderly patents.     

亚临床甲状腺功能减退症

亚临床甲状腺功能减退症（甲减）是一种亚临床甲状腺疾病。诊断标准是血清促甲状腺激素（TSH）水平高于正常上限而游离T4水平尚在正常范围。目前全世界亚临床甲减的平均患病率为4％-10％,主要发生在女性和老年人群。桥本甲状腺炎是最常见的病因。其主要的临床危害包括引起血脂异常、导致动脉粥样硬化和冠心病、影响认知功能,还可导致不孕和流产。治疗主要针对血清TSH〉10ml U／L的患者,应用左旋-T4替代治疗。对于血清TSH4～10ml U／L,特别是甲状腺自身抗体阳性者需密切监测。此外,对妊娠期亚临床甲减患者的治疗要求控制TSH〈2．5ml U／L。     

亚临床甲状腺功能减退症

亚临床甲状腺功能减退症(甲减)是一种业临床甲状腺疾病.诊断标准是血清促甲状腺激素(TSH)水平高于正常上限而游离T4水平尚在正常范围.目前全世界业临床甲减的平均患病率为4%～10%,主要发生在女性和老年人群.桥本甲状腺炎是最常见的病因.其卡要的临床危害包括引起血脂异常、导致动脉粥样硬化和,冠心病、影响认知功能,还可导致不孕和流产.治疗主要针对血清TSH10 mIU/L的患者,应用左旋-T4替代治疗.对于血清TSH 4～10 mIU/L,特别是甲状腺自身抗体阳性者需密切监测.此外,对妊娠期亚临床甲减患者的治疗要求控制TSH<2.5 mlU/L.     

Subclinical hypothyroidism and the risk of heart failure, other cardiovascular events, and death

BACKGROUND: Subclinical hypothyroidism has been associated with systolic and diastolic cardiac dysfunction and an elevated cholesterol level, but data on cardiovascular outcomes and death are limited. METHODS: We studied 2730 men and women, aged 70 to 79 years, with baseline thyrotropin (TSH) measurements and 4-year follow-up data to determine whether subclinical hypothyroidism was associated with congestive heart failure (CHF), coronary heart disease, stroke, peripheral arterial disease, and cardiovascular-related and total mortality. After the exclusion of participants with abnormal thyroxine levels, subclinical hypothyroidism was defined as a TSH level of 4.5 mIU/L or greater, and was further classified according to TSH levels (4.5-6.9, 7.0-9.9, and > or = 10.0 mIU/L). RESULTS: Subclinical hypothyroidism was present in 338 (12.4%) of the participants. Compared with euthyroid participants, CHF events occurred more frequently among those with a TSH level of 7.0 mIU/L or greater (35.0 vs 16.5 per 1000 person-years; P = .006), but not among those with TSH levels between 4.5 and 6.9 mIU/L. In multivariate analyses, the risk of CHF was higher among those with high TSH levels (TSH of 7.0-9.9 mIU/L: hazard ratio, 2.58 [95% confidence interval, 1.19-5.60]; and TSH of > or = 10.0 mIU/L: hazard ratio, 3.26 [95% confidence interval, 1.37-7.77]). Among the 2555 participants without CHF at baseline, the hazard ratio for incident CHF events was 2.33 (95% confidence interval, 1.10-4.96; P = .03) in those with a TSH of 7.0 mIU/L or greater. Subclinical hypothyroidism was not associated with increased risk for coronary heart disease, stroke, peripheral arterial disease, or cardiovascular-related or total mortality. CONCLUSIONS: Subclinical hypothyroidism is associated with an increased risk of CHF among older adults with a TSH level of 7.0 mIU/L or greater, but not with other cardiovascular events and mortality. Further investigation is warranted to assess whether subclinical hypothyroidism causes or worsens preexisting heart failure.     

亚临床甲状腺功能减退症与妊娠

妊娠期亚临床甲状腺功能减退症(甲减)的患病率较高,美国流行病调查显示约占妊娠妇女的2%~5%。多项研究证实妊娠妇女患亚临床甲减可影响其后代的智力发育,并可能产生各种产科并发症。妊娠期亚临床甲减影响后代智力发育的确切机制尚不清楚。专家多主张对血清促甲状腺激素升高的孕妇或计划怀孕的妇女,应及时给予左旋甲状腺素治疗。但是对于妊娠期妇女是否应常规进行亚临床甲减的筛查仍存在争议,另外左旋甲状腺素替代治疗的效果还需大量循证医学资料来证实。     

亚临床甲状腺功能减退与动脉粥样硬化

亚临床甲状腺功能减退(SCH)又称轻度甲状腺功能衰竭,主要诊断依据是血清促甲状腺激素(TSH)增高,而血清游离甲状腺素(FT4)正常,同时应排除以下引起TSH增高的情况:甲状腺功能减低患者左旋甲状腺素(L-T4)替代剂量不足,严重疾患恢复期患者暂时TSH升高,破坏性甲状腺炎恢复期,未经治疗的原发肾上腺皮质功能不全,注射TSH的患者.     

Subclinical hypothyroidism is associated with a low-grade inflammation, increased triglyceride levels and predicts cardiovascular disease in males below 50 years

OBJECTIVE: Mild thyroid failure is associated with an increased risk for development of atherosclerosis, but whether subclinical hypothyroidism is related to risk for cardiovascular disease is controversial. The purpose of the present study was to examine a possible association between subclinical hypothyroidism and cardiovascular disease. DESIGN: Cross-sectional study of a general population. PATIENTS: Twelve hundred and twelve subjects, men and women, between 20 and 69 years old without thyroid disease not treated with drugs interfering with thyroid function or analysis of TSH were included. MEASUREMENTS: Clinical signs of cardiovascular disease based on a questionnaire and medical records and laboratory analysis of lipids, atherothrombotic risk markers, C-reactive protein and TSH. RESULTS: The main findings were a high incidence of subclinical hypothyroidism (19.7%) in a general population. Subclinical hypothyroidism was associated with higher concentrations of triglycerides and C-reactive protein. Below 50 years of age cardiovascular disease was more frequent in males with subclinical hypothyroidism compared to euthyroid males. Subclinical hypothyroidism was a predictor of cardiovascular disease in males below 50 years with an odds ratio of 3.4 (95% confidence interval 1.6-6.8) for developing cardiovascular disease compared to euthyroid age-matched males. CONCLUSION: Our study demonstrates that patients with subclinical hypothyroidism have increased levels of triglycerides and signs of low-grade inflammation (raised C-reactive protein levels) and that subclinical hypothyroidism might be a risk factor for development of cardiovascular disease in younger males.     

亚临床甲状腺功能减退症与缺血性卒中

亚临床甲状腺功能减退症（subclinicalhypothyroidism,SCH）可能与颈动脉粥样硬化、血脂异常、高血压、高同型半胱氨酸血症、冠心病之间存在关联,而这些因素常被视为缺血性卒中的危险因素。 SCH与卒中发病风险之间的相关性目前尚不清楚,SCH可增高卒中风险的假设未能得到证实,甚至有研究表明SCH可能对卒中预后产生有利影响。文章对SCH与卒中危险因素、卒中风险和预后的关系进行了综述。     

Subclinical hypothyroidism, arterial stiffness, and myocardial reserve

CONTEXT: Subclinical hypothyroidism (SCH) is associated with increased risk of cardiac disease; its impact on arterial function is less clear. OBJECTIVE: The objective of the study was the assessment of arterial and cardiac function. DESIGN: The study was a 6-month controlled observational study using pulse wave analysis and tissue Doppler dobutamine stress echocardiography. SETTING: The study was conducted at a thyroid clinic. PATIENTS: Nineteen female SCH patients with raised TSH, normal free T(4), and no cardiovascular disease [aged 49.2 +/- 3.8 yr; body mass index (BMI) 29.9 +/- 6.7 kg/m(2)] were recruited from the thyroid clinic, and 10 female controls (aged 50.2 +/- 3.4 yr; BMI 29.7 +/- 7.2 kg/m(2)) also participated in the study. INTERVENTIONS: Incremental doses of l-thyroxine were used. MAIN OUTCOME MEASURES: Indices of vascular stiffness and left ventricular echocardiographic function were measured. RESULTS: Baseline augmentation gradient was elevated in SCH, compared with controls [10.3 +/- 5.1 (sd) mm Hg vs. 8.0 +/- 4.2, P < 0.05]; when euthyroid (mean T(4) dose 114 mug/d), it fell to 8.8 +/- 5.3 mm Hg (P < 0.05). Heart rate-corrected augmentation index was 26.7 +/- 9.9 vs. 18.8 +/- 9.9% (P < 0.02), falling to 19.7 +/- 9.6% (P < 0.001) after treatment. Time of travel of the reflected wave was 139.3 +/- 11.7 msec, compared with 141.5 +/- 8.8 msec in controls (P < 0.05), increasing to 144.9 +/- 11.9 msec (P < 0.05). There were no differences in resting global, regional left ventricular function, or regional myocardial velocities during maximal dobutamine stress between SCH patients and controls, or in treated patients, compared with baseline. CONCLUSIONS: Arterial stiffness was increased in SCH and improved with l-thyroxine, which may be beneficial, whereas myocardial functional reserve was similar to controls and remained unaltered after treatment.     

儿童亚临床甲状腺功能减退症

以往研究多关注成年人亚临床甲状腺功能减退症(SH),但因它对儿童神经心理发育有潜在影响,可能影响到儿童的认知水平和智力发育,从而影响其成年后生活质量,因而对儿童SH的研究受到关注.目前对其发病机制的研究较为清楚,然而关于如何进行治疗还存在争议,是否需要甲状腺素替代治疗尚无定论.     

脂质代谢异常与慢性肾脏病合并心血管疾病的研究进展

慢性肾脏病(CKD)的患病率逐年上升,而心血管疾病(CVD)是导致其死亡的主要原因。CKD患者往往同时合并脂质代谢异常,这是促进CVD发生发展的重要因素,但CKD患者的脂质代谢异常与CVD发病率和死亡率之间的关系有其特殊性,各类降脂治疗能否有效改善CKD患者的CVD也存在争议。因此,文章就脂质代谢异常与CKD患者合并CVD发生的病理生理机制及相关性作一综述,这对降低CKD患者CVD发生率及改善患者预后具有十分重要的意义。