Mark Vanderpump

The influence of age on the relationship between subclinical hypothyroidism and ischemic heart disease: a metaanalysis.

CONTEXT Subclinical hypothyroidism (SCH) is a common condition that has been associated with ischemic heart disease (IHD) in some, but not all, studies. This may be due to differences in study design and the characteristics of participants. OBJECTIVE Our objective was to investigate whether age and gender influence IHD prevalence, incidence, and mortality in people with SCH. DATA SOURCES Computerized (PubMed, EMBASE, and Cochrane Library) and manual searches of the literature to May 2007, published in English, were performed. STUDY SELECTION Epidemiological studies that quantified thyroid status and IHD events in adults were performed. DATA EXTRACTION Two authors independently reviewed articles and abstracted data. Results were compared across two groups based on the minimum age of participants studied (younger than 65 yr and 65 yr or older). DATA SYNTHESIS There were 15 studies included for analysis with 2,531 SCH participants and 26,491 euthyroid individuals. IHD incidence and prevalence were higher in SCH subjects compared with euthyroid participants from studies including those younger than 65 yr, but not studies of subjects aged older than 65 yr [odds ratio (95% confidence interval)]: 1.57 (1.19-2.06) vs. 1.01 (0.87-1.18) and 1.68 (1.27-2.23) vs. 1.02 (0.85-1.22), respectively. Cardiovascular/all-cause mortality was also elevated in participants from the younger than 65-yr studies, but not from the studies of older people: odds ratio 1.37 (1.04-1.79) vs. 0.85 (0.56-1.29). Prevalent IHD was higher in SCH participants of both genders, although this was statistically significant only in women. CONCLUSIONS SCH is associated with increased IHD (both prevalence and incidence) and cardiovascular mortality only in subjects from younger populations. These data suggest that increased vascular risk may only be present in younger individuals with SCH.

Epidemiology and Prevention of Clinical and Subclinical Hypothyroidism

Iodine deficiency is the most common cause of hypothyroidism worldwide. In persons living in iodine-replete areas, causes are congenital, spontaneous because of chronic autoimmune disease (atrophic autoimmune thyroiditis or goitrous autoimmune thyroiditis [Hashimotos thyroiditis]), or iatrogenic because of goitrogens, drugs, or destructive treatment for thyrotoxicosis. Screening for congenital hypothyroidism exists and its use prevents mental retardation. The prevalence of spontaneous hypothyroidism is between 1% and 2% and is more common in older women and 10 times more common in women than in men. A significant proportion of subjects have asymptomatic chronic autoimmune thyroiditis and 8% of women (10% of women over 55 years of age) and 3% of men have subclinical hypothyroidism. Approximately one third of patients with newly diagnosed overt hypothyroidism have received destructive therapy for hyperthyroidism and indefinite surveillance is required. There is not much that can be done to prevent the occurrence of spontaneous autoimmune hypothyroidism, but if identified early, something can be done to prevent progression to overt disease. Controversy exists as to whether healthy adults would benefit from screening for autoimmune thyroid disease because a significant proportion of subjects tested will have evidence of mild thyroid failure. Case finding in women at menopause or visiting a primary care physician with nonspecific symptoms appears justified.

The Incidence of Ischemic Heart Disease and Mortality in People with Subclinical Hypothyroidism: Reanalysis of the Whickham Survey Cohort

CONTEXT The Whickham Survey evaluated vascular events over 20 yr in community-dwelling subjects stratified by thyroid function and thyroid autoantibody status. No association between ischemic heart disease (IHD) and a composite autoimmune thyroid disease group, comprising individuals with subclinical hypothyroidism (SCH), with positive thyroid antibodies or those using levothyroxine, was found. This result appears to be at odds with the findings of other cohort studies. OBJECTIVE The objective of the study was to evaluate incident IHD and mortality in participants in relation to their thyroid status. OUTCOMES, DESIGN, AND PARTICIPANTS: Data were reanalyzed assessing incident IHD events and mortality during 20 yr of follow-up in individuals with endogenous SCH (n = 97; TSH 6.0-15 mIU/liter) vs. the euthyroid group (n = 2279), who were IHD free at baseline. RESULTS Incident IHD was significantly higher in the SCH group [adjusted hazard ratio 1.76 (95% confidence interval 1.15-2.71); P = 0.01]. IHD mortality was also increased in the SCH group [hazard ratio of 1.79 (1.02-3.56); P = 0.05]. These findings lost their significance when subsequent treatment with levothyroxine was excluded from the regression model. There was no difference in all-cause mortality between the groups. CONCLUSION In the Whickham Survey, there is an association between incident IHD events and IHD-related mortality with SCH over the 20 yr of follow-up. Furthermore, subsequent treatment of SCH with levothyroxine appears to attenuate IHD-related morbidity and mortality, and this may explain why some other longitudinal studies of SCH have not shown such an association; properly designed controlled trials of treatment of SCH are required to answer this question definitively.

UK guidelines for the management of pituitary apoplexy

Classical pituitary apoplexy is a medical emergency and rapid replacement with hydrocortisone maybe life saving. It is a clinical syndrome characterized by the sudden onset of headache, vomiting, visual impairment and decreased consciousness caused by haemorrhage and/or infarction of the pituitary gland. It is associated with the sudden onset of headache accompanied or not by neurological symptoms involving the second, third, fourth and sixth cranial nerves. If diagnosed patients should be referred to a multidisciplinary team comprising, amongst others, a neurosurgeon and an endocrinologist. Apart from patients with worsening neurological symptoms in whom surgery is indicated, it is unclear currently for the majority of patients whether conservative or surgical management carries the best outcome. Post apoplexy, there needs to be careful monitoring for recurrence of tumour growth. It is suggested that further trials be carried out into the management of pituitary apoplexy to optimize treatment.

POPULATION SCREENING FOR AUTOIMMUNE THYROID DISEASE

Whether or not healthy adults in the community would benefit from screening for autoimmune thyroid disease is controversial. Although the prevalence of unsuspected overt thyroid disease is low, a significant proportion of subjects tested will have evidence of mild thyroid failure or excess. This article assesses whether subclinical thyroid disease is of sufficient clinical importance to warrant screening and, once detected and confirmed, to justify therapy. Population screening for autoimmune thyroid disease is assessed against recently revised screening criteria, using data from epidemiologic studies. Recommendations are proposed that may be applied in any iodine-replete community.

Benzofuran derivatives and the thyroid

Amiodarone and dronedarone are two clinically important benzofuran derivatives. Amiodarone has been used widely for treating resistant tachyarrhythmias in the past three decades. However amiodarone and its main metabolically active metabolite desethylamiodarone can adversely affect many organs, including the thyroid gland. Amiodarone‐induced thyroid disorders are common and often present as a management challenge for endocrinologists. The pathogenesis of amiodarone‐induced thyroid dysfunction is complex but the inherent effects of the drug itself as well as its high iodine content appear to play a central role. The non‐iodinated dronedarone also exhibits anti‐arrhythmic properties but appears to be less toxic to the thyroid. This review describes the biochemistry of benzofuran derivatives, including their pharmacology and the physiology necessary for understanding the cellular mechanisms involved in their actions. The known effects of these compounds on thyroid action are described. Recommendations for management of amiodarone‐induced hypothyroidism and thyrotoxicosis are suggested. Dronedarone appears to be an alternative but less‐effective anti‐arrhythmic agent and it does not have adverse effects on thyroid function. It may have a future role as an alternative agent in patients being considered for amiodarone therapy especially those at high risk of developing thyroid dysfunction but not in severe heart failure.

Thyroid Function Within the Normal Range and Risk of Coronary Heart Disease: An Individual Participant Data Analysis of 14 Cohorts

IMPORTANCE Some experts suggest that serum thyrotropin levels in the upper part of the current reference range should be considered abnormal, an approach that would reclassify many individuals as having mild hypothyroidism. Health hazards associated with such thyrotropin levels are poorly documented, but conflicting evidence suggests that thyrotropin levels in the upper part of the reference range may be associated with an increased risk of coronary heart disease (CHD). OBJECTIVE To assess the association between differences in thyroid function within the reference range and CHD risk. DESIGN, SETTING, AND PARTICIPANTS Individual participant data analysis of 14 cohorts with baseline examinations between July 1972 and April 2002 and with median follow-up ranging from 3.3 to 20.0 years. Participants included 55,412 individuals with serum thyrotropin levels of 0.45 to 4.49 mIU/L and no previously known thyroid or cardiovascular disease at baseline. EXPOSURES Thyroid function as expressed by serum thyrotropin levels at baseline. MAIN OUTCOMES AND MEASURES Hazard ratios (HRs) of CHD mortality and CHD events according to thyrotropin levels after adjustment for age, sex, and smoking status. RESULTS Among 55,412 individuals, 1813 people (3.3%) died of CHD during 643,183 person-years of follow-up. In 10 cohorts with information on both nonfatal and fatal CHD events, 4666 of 48,875 individuals (9.5%) experienced a first-time CHD event during 533,408 person-years of follow-up. For each 1-mIU/L higher thyrotropin level, the HR was 0.97 (95% CI, 0.90-1.04) for CHD mortality and 1.00 (95% CI, 0.97-1.03) for a first-time CHD event. Similarly, in analyses by categories of thyrotropin, the HRs of CHD mortality (0.94 [95% CI, 0.74-1.20]) and CHD events (0.97 [95% CI, 0.83-1.13]) were similar among participants with the highest (3.50-4.49 mIU/L) compared with the lowest (0.45-1.49 mIU/L) thyrotropin levels. Subgroup analyses by sex and age group yielded similar results. CONCLUSIONS AND RELEVANCE Thyrotropin levels within the reference range are not associated with risk of CHD events or CHD mortality. This finding suggests that differences in thyroid function within the population reference range do not influence the risk of CHD. Increased CHD risk does not appear to be a reason for lowering the upper thyrotropin reference limit.

Thyroid Antibody Status, Subclinical Hypothyroidism, and the Risk of Coronary Heart Disease: An Individual Participant Data Analysis

CONTEXT Subclinical hypothyroidism has been associated with increased risk of coronary heart disease (CHD), particularly with thyrotropin levels of 10.0 mIU/L or greater. The measurement of thyroid antibodies helps predict the progression to overt hypothyroidism, but it is unclear whether thyroid autoimmunity independently affects CHD risk. OBJECTIVE The objective of the study was to compare the CHD risk of subclinical hypothyroidism with and without thyroid peroxidase antibodies (TPOAbs). DATA SOURCES AND STUDY SELECTION A MEDLINE and EMBASE search from 1950 to 2011 was conducted for prospective cohorts, reporting baseline thyroid function, antibodies, and CHD outcomes. DATA EXTRACTION Individual data of 38 274 participants from six cohorts for CHD mortality followed up for 460 333 person-years and 33 394 participants from four cohorts for CHD events. DATA SYNTHESIS Among 38 274 adults (median age 55 y, 63% women), 1691 (4.4%) had subclinical hypothyroidism, of whom 775 (45.8%) had positive TPOAbs. During follow-up, 1436 participants died of CHD and 3285 had CHD events. Compared with euthyroid individuals, age- and gender-adjusted risks of CHD mortality in subclinical hypothyroidism were similar among individuals with and without TPOAbs [hazard ratio (HR) 1.15, 95% confidence interval (CI) 0.87-1.53 vs HR 1.26, CI 1.01-1.58, P for interaction = .62], as were risks of CHD events (HR 1.16, CI 0.87-1.56 vs HR 1.26, CI 1.02-1.56, P for interaction = .65). Risks of CHD mortality and events increased with higher thyrotropin, but within each stratum, risks did not differ by TPOAb status. CONCLUSIONS CHD risk associated with subclinical hypothyroidism did not differ by TPOAb status, suggesting that biomarkers of thyroid autoimmunity do not add independent prognostic information for CHD outcomes.

Description and validation of a Markov model of survival for individuals free of cardiovascular disease that uses Framingham risk factors

BackgroundEstimation of cardiovascular disease risk is increasingly used to inform decisions on interventions, such as the use of antihypertensives and statins, or to communicate the risks of smoking. Crude 10-year cardiovascular disease risk risks may not give a realistic view of the likely impact of an intervention over a lifetime and will underestimate of the risks of smoking. A validated model of survival to act as a decision aid in the consultation may help to address these problems. This study aims to describe the development of such a model for use with people free of cardiovascular disease and evaluates its accuracy against data from a United Kingdom cohort.MethodsA Markov cycle tree evaluated using cohort simulation was developed utilizing Framingham estimates of cardiovascular risk, 1998 United Kingdom mortality data, the relative risk for smoking related non-cardiovascular disease risk and changes in systolic blood pressure and serum total cholesterol total cholesterol with age. The models estimates of survival at 20 years for 1391 members of the Whickham survey cohort between the ages of 35 and 65 were compared with the observed survival at 20-year follow-up.ResultsThe model estimate for survival was 75% and the observed survival was 75.4%. The correlation between estimated and observed survival was 0.933 over 39 subgroups of the cohort stratified by estimated survival, 0.992 for the seven 5-year age bands from 35 to 64, 0.936 for the ten 10 mmHg systolic blood pressure bands between 100 mmHg and 200 mmHg, and 0.693 for the fifteen 0.5 mmol/l total cholesterol bands between 3.0 and 10.0 mmol/l. The model significantly underestimated mortality in those people with a systolic blood pressure greater than or equal to 180 mmHg (p = 0.006).The average gain in life expectancy from the elimination of cardiovascular disease risk as a cause of death was 4.0 years for all the 35 year-old men in the sample (n = 24), and 1.8 years for all the 35 year-old women in the sample (n = 32).ConclusionsThis model accurately estimates 20-year survival in subjects from the Whickham cohort with a systolic blood pressure below 180 mmHg.

The relation between thyroid function and anemia: a pooled analysis of individual participant data.

Context Anemia and thyroid dysfunction often co-occur, and both increase with age. Human data on relationships between thyroid disease and anemia are scarce. Objective To investigate the cross-sectional and longitudinal associations between clinical thyroid status and anemia. Design Individual participant data meta-analysis. Setting Sixteen cohorts participating in the Thyroid Studies Collaboration (n = 42,162). Main Outcome Measures Primary outcome measure was anemia (hemoglobin <130 g/L in men and <120 g/L in women). Results Cross-sectionally, participants with abnormal thyroid status had an increased risk of having anemia compared with euthyroid participants [overt hypothyroidism, pooled OR 1.84 (95% CI 1.35 to 2.50), subclinical hypothyroidism 1.21 (1.02 to 1.43), subclinical hyperthyroidism 1.27 (1.03 to 1.57), and overt hyperthyroidism 1.69 (1.00 to 2.87)]. Hemoglobin levels were lower in all groups compared with participants with euthyroidism. In the longitudinal analyses (n = 25,466 from 14 cohorts), the pooled hazard ratio for the risk of development of anemia was 1.38 (95% CI 0.86 to 2.20) for overt hypothyroidism, 1.18 (1.00 to 1.38) for subclinical hypothyroidism, 1.15 (0.94 to 1.42) for subclinical hyperthyroidism, and 1.47 (0.91 to 2.38) for overt hyperthyroidism. Sensitivity analyses excluding thyroid medication or high levels of C-reactive protein yielded similar results. No differences in mean annual change in hemoglobin levels were observed between the thyroid hormone status groups. Conclusion Higher odds of having anemia were observed in participants with both hypothyroid function and hyperthyroid function. In addition, reduced thyroid function at baseline showed a trend of increased risk of developing anemia during follow-up. It remains to be assessed in a randomized controlled trial whether treatment is effective in reducing anemia.