THE PREVALENCE OF SUBCLINICAL HYPOTHYROIDISM IN THE POPULATION OF ELDERLY NURSING HOME RESIDENTS IN ZAGREB

The aim of the study was to investigate the prevalence of thyroid dysfunction, positive thyroid peroxidase antibodies (TPOAb) and hypercholesterolemia in elderly and younger subjects, and the association of subclinical hypothyroidism with hypercholesterolemia. The study included 204 elderly (136 females and 68 males, age median 71, range 60-92 years), and 83 younger control subjects (63 females and 20 males, age median 45, range 19-55 years). Subjects with prior thyroid dysfunction were excluded. Serum thyrotropin (TSH), free triiodothyronine (FT3), free thyroxine (FT4), TPOAb, total cholesterol, height and weight were measured. Mann-Whitney, χ²-test and Student's t-test were used on statistical analysis. The prevalence of subclinical hypothyroidism (TSH >5 mU/L) in elderly was 7.4% vs. 3.6% in younger subjects, with the highest prevalence of 8.8% in elderly women vs. 4.8% in younger women, and 4.4% in elderly men. The prevalence of hypothyroidism and subclinical hyperthyroidism in elderly subjects was 0.5% and 1.5%, respectively. In women with subclinical hypothyroidism, the prevalence of TPOAb was 77% in elderly women and 67% in younger women (overall 19.9% in elderly and 14.3% in younger women). The mean FT3 level was lower in elderly women as compared with elderly men (p<0.01) and younger women (p<0.05). The mean cholesterol level was higher in elderly subjects in comparison with younger ones (p<0.01), and in elderly women vs. elderly men (p<0.01), but without difference between subclinical hypothyroidism and euthyroid subjects (6.0 mmol/L). In conclusion, subclinical hypothyroidism is the most prevalent thyroid dysfunction in elderly, with the highest prevalence in elderly women, and autoimmune thyroiditis is the most common etiology. Hypercholesterolemia was more related to older age, especially elderly females, but not influenced by subclinical hypothyroidism.