Cardiovascular outcomes in subclinical thyroid disease: an update

PURPOSE OF REVIEW

Subclinical thyroid disease is defined by a thyroid stimulating hormone (TSH) level outside of the normal range with normal circulating thyroid hormone levels. Excess adverse cardiovascular outcomes have been observed in certain patient populations with subclinical hypothyroidism (SCH) and hyperthyroidism (SCHr). The role of thyroid hormone and antithyroid treatments for subclinical thyroid disease remains debated.

RECENT FINDINGS

Cardiovascular disease appears to be a major mediator of all-cause mortality in patients with SCH, in particular those aged at least 60 years of age. In contrast, pooled clinical trial results did not find that levothyroxine reduced the incidence of cardiovascular events or mortality in this patient population. The association between SCHr and atrial fibrillation is well established; however, a 5-year follow-up of older patients with mild (TSH 0.1-0.4 mIU/l) SCHr found no increased incidence of atrial fibrillation. Separately, SCHr was associated with derangements in endothelial progenitor cell function that may underlie vascular disease independent from effects on cardiac function.

SUMMARY

The impact of treatment of subclinical thyroid disease on cardiovascular outcomes remains uncertain. Additional prospective and trial data are needed to evaluate treatment effects on cardiovascular outcomes in younger populations.

Thyrotrophin levels and coronary artery calcification: Cross-sectional results of the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil)

OBJECTIVE

There is little information about the association between thyrotrophin (TSH) levels and coronary artery calcification (CAC). Our aim was to analyse the association between TSH quintiles and subclinical atherosclerosis measured by CAC, using baseline data from the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil).

DESIGN

Cross-sectional study.

PATIENTS

We excluded individuals using medications that affect thyroid function and who self-reported cardiovascular disease. We included euthyroid subjects and individuals with subclinical hypothyroidism (SCHypo) and subclinical hyperthyroidism (SCHyper). Logistic regression models evaluated CAC >100 Agatston units as the dependent variable, and increasing quintiles of TSH as the independent variable, adjusted for demographic and cardiovascular risk factors.

RESULTS

Our sample included 3836 subjects, mean age 49 years (interquartile range 44-56); 1999 (52.1%) were female, 3551 (92.6%) were euthyroid, 239 (6.2%) had SCHypo and 46 (1.2%) had SCHyper. The frequency of women, White people and never smokers as well as body mass index and insulin resistance increased according to quintiles. The 1st quintile for TSH (0-0.99 mIU/L) was associated with CAC >100, using the 3rd quintile (1.39-1.85 mIU/L) as reference (adjusted OR=1.57, 95% CI: 1.05-2.35, P=.027), but no association was shown for the 5th quintile (2.68-35.5 mIU/L) compared to the 3rd. Restricting the analysis to euthyroid subjects did not change the results. For women, but not for men, we observed a U-shaped curve with 1st and 5th TSH quintiles associated with CAC>100.

CONCLUSION

Low and low-normal (1st quintile) TSH levels were associated with CAC>100 Agatston units in a sample with subclinical thyroid disorders and euthyroid subjects.

Screening for thyroid disease: defining high-risk populations

The pros and cons of population screening for thyroid disease have been hotly debated over the past several decades. This article addresses the issue from the point of view of the potential benefit of screening, that is, disease detection. Earlier diagnoses of hypothyroidism, hyperthyroidism, thyroid nodules, thyroid cancer and so on, with implementation of the indicated diagnostic and therapeutic interventions, avoid the adverse consequences of unrecognized and untreated progressive disease. Arguments against screening and case-finding often focus on cost considerations. To achieve the greatest yield at the lowest cost, our emphasis is on vulnerable populations with associated risk factors, and special situations such as pregnancy.

Chronic fatigue: is it endocrinology?

Fatigue and stress-related illnesses often become diagnoses of exclusion after extensive investigation. 'Tired all the time' is a frequent reason for referral to the endocrine clinic, the implicit question being--is there a subtle endocrine pathology contributing to the patient's symptoms? Often initial assessment suggests not but there are no clear data to address the question of whether overt pathology will develop in the future. This study observed outcomes after five years in 101 consecutive and unselected referrals to secondary care for 'fatigue?cause', where initial assessment did not suggest treatable endocrine pathology. The findings suggest that the clinical diagnosis of fatigue, based on history and tests to exclude anaemia, hypothyroidism and diabetes, is secure: these patients do not subsequently demonstrate excess morbidity and mortality, and their presenting symptoms are not early features of significant endocrine pathology.