[Thyroid function and dysfunction in the elderly]

[Thyroid in the elderly (Part 1)]

Aging is associated with changes in thyroid function at several levels of regulation. Thyroid hormones levels are usually within the lower part of normal values reported in the general population. Two changes in aging are of clinical importance: a shift in the distribution of TSH levels, the 97.5th percentile of the TSH distribution being within 6 μUI/ml after 70 years and within 7.5 μUI/ml in subjects older than 80 instead of 4.5 μU/ml in the general population, and an increased prevalence of thyroid nodularity, requiring reliable and non-invasive methods of investigation in older people. Lastly, aging may be associated with comorbidities, high risk of drug interactions and under nutrition, which may make difficult the interpretation of laboratory data and in some cases induce iatrogenic thyroid diseases. Considering the high prevalence of the thyroid diseases in older patients and a better understanding of the physiopathological hormonal variations with the ageing, it seemed useful to propose a review to help the clinician in the care of these situations.

Manifestations et risques cardiovasculaires des dysthyroïdies infracliniques

PURPOSE

To clarify the importance of cardiovascular symptoms and risks in subclinical dysthyroidism in order to define the best way of treatment and follow-up.

CURRENT KNOWLEDGE AND KEY POINTS

Subclinical dysthyroidism is defined by abnormal circulating TSH values in face and normal free thyroid hormones levels, in asymptomatic individuals. If the cardiovascular effects of overt hyperthyroidism are well documented, the relation between subclinical dysthyroidism and the heart is not well established. Subclinical hyperthyroidism may be caused by the same thyroid disorders that results in overt hyperthyroidism, but the most common cause is excessive dosage in levothyroxine. The most frequent cardias complication of subclinical hyperthyroidism is atrial fibrillation. Recently minimal alterations of myocardial function have also been described. In most patients, one tries to return to euthyroidism in order to prevent cardiovascular complications. Subclinical hypothyroidism is 3 to 10 times more frequent, especially in women after 60 years. Subtle modifications of cardiac function and lipid metabolism and an increased risk of atherosclerosis have been described in this condition. There is still debate about the decision to treat or not to treat these patients.

FUTURE PROSPECTS AND PROJECTS

Until now, treatment of subclinical dysthyroidism is mainly based upon experiences and convictions to physicians. Prospective studies are necessary to assess the true benefits and risks of either early treatment or therapeutic abstention with regular clinical and biological follow up. In such studies, patients should be separated according to age and the nature (endogenous or exogenous) of dysthyroidism.