Subclinical hyperthyroidism is the most prevalent thyroid dysfunction in older Italians and is associated with cognitive impairment

CLINICAL THYROIDOLOGY  JANUARY 2009 18 VOLUME 21  ISSUE 1 A value less than 24 was considered to indicate cognitive impairment. Other information on demographics, smoking, and the use of medication were collected using standardized questionnaires. Weight, body-mass index (BMI), and the level of physical activity and exercise, nutrition and disease were also evaluated by standardized questionnaires. Participants were classified according to TSH and FT4 and FT3 concentrations into five categories: (1) overt hypothyroidism (TSH >4.68 μIU/ml, FT4 <0.78 ng/dl); (2) subclinical hypothyroidism (TSH >4.68 μIU/ml, FT4 = 0.77 to 2.19 ng/dl); (3) euthyroidism (TSH = 0.46 to 4.68 μIU/ml), (4) subclinical hyperthyroidism (TSH <0.46 μIU/ml, FT4 = 0.77 to 2.19 ng/dl, FT3 = 2.77 to 5.27 pg/ml); and (5) overt hyperthyroidism (TSH <0.46 μIU/ml, FT4 >2.19 ng/dl, FT3 >.27 pg/ml). Four patients with low T3 syndrome with normal FT3 and TSH levels were excluded from the analysis.