The prevalence of thyroid dysfunction in elderly cardiology patients with mild excessive iodine intake in the urban area of São Paulo

Abstract

Objectives: To evaluate the prevalence of thyroid dysfunction in elderly cardiac patients in an outpatient setting.

Subjects and methods: A total of 399 consecutive patients (268 women, age range 60-92 years) who were followed at Heart Institute were evaluated for thyroid dysfunction with serum free T4, TSH, anti-Peroxidase antibodies, urinary iodine excretion measurements and thyroid ultrasound.

Results: Hyperthyroidism (overt and subclinical) was present in 29 patients (6.5%), whereas hypothyroidism (overt and subclinical) was found in 32 individuals (8.1%). Cysts were detected in 11 patients (2.8%), single nodules were detected in 102 (25.6%), and multinodular goiters were detected in 34 (8.5%). Hashimoto's thyroiditis was present in 16.8% patients, most of whom were women (83.6%). The serum TSH increased with age and was significantly higher (p= <0.01) in patients, compared to the normal control group. No significant differences in serum TSH and free T4 values were observed when patients with atrial fibrillation (AF) where compared with those without arrhythmia. The median urinary iodine levels were 210 microg/L (40-856 microg/L), and iodine levels were higher in men than in women (p<0.01). Excessive iodine intake (urinary iodine >300 microg/L) was observed in one-third of patients (30.8%).

Conclusions: Elderly patients have a higher prevalence of both hypo- and hyperthyroidism as well as thyroid nodules when compared with the general population. About one-third of the older patients had elevated urinary secretion of iodine and a higher prevalence of chronic Hashimoto's thyroiditis. It is recommended that ultrasonographic studies, tests for thyroid function and autoimmunity should be evaluated in elderly patients.

Figure 1 -

TSH levels within age groups. Note the increasing TSH values with age in men and women (p=<0.02)

Figure 2 -

Thyroid volume compared with different ultrasonographic findings. N: no abnormality; C: cysts; UN: single nodule; and MN: multinodular goiter. Note that patients with thyroid nodules had a significantly increased thyroid volume (* p<0.01)

Figure 3 -

Distribution of iodine concentration in the studied population. The median urinary excretion was 210 μg/L. Note that one-third of the subjects had an excessive iodine excretion (>300 μg/L)