Changes of thyroid function is independently associated with cognitive function in elderly subjects with subclinical hypothyroidism: A result from a population-based longitudinal follow-up study of KLoSHA

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: SUN 414-431-HPT Axis Biology
Sunday, June 16, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board SUN-419
Jae Hoon Moon*, Tae Hui Kim, Tae Hyuk Kim, Hoonsung Choi, Sun Wook Cho, Kyung Won Kim, Young Joo Park, Ka Hee Yi, Ki Woong Kim, Do Joon Park and Hak C Jang
Seoul National University College of Medicine, Seoul, South Korea
Objectives: Overt hypothyroidism has been well known to include widespread cognitive deficit. However, there are still controversies regarding cognitive effects of subclinical hypothyroidism (SCH) and the treatment of SCH. This study is a population-based longitudinal follow-up study to investigate the relationship between thyroid function and cognitive function in Korean elderly subjects.

Subjects and Methods: This study was conducted as a part of the Korean Longitudinal Study on Health and Aging (KLoSHA). Among 992 participants who were initially enrolled in this cohort, 411 participants who completed 5-year follow-up evaluation were analyzed in the present study. Cognitive function was evaluated using the Korean version of the consortium to establish a registry for Alzheimer’s disease assessment battery (CERAD-K), the frontal assessment battery (FAB), the revised Hasegawa dementia scale (HDS-R), and digit-span test (DST). Anthropometric and other metabolic parameter including thyroid function were also evaluated. 

Results: In 325 subjects with normal thyroid function at baseline evaluation, none of evaluated cognitive domains were associated with free thyroxine (fT4) and thyroid stimulating hormone (TSH) levels at a single time-point (baseline and follow-up). The change of fT4 and TSH between baseline and follow-up were not associated with cognitive function in this group. In 68 subjects with SCH at baseline, none of cognitive domains were independently associated with fT4 or TSH at a single time point. However, the change in TSH (ΔTSH) was associated with all investigated cognitive domains except one domain of CERAD-K (constructional recall test) and FAB in this group. Moreover, 3 domains of CERAD-K (mini-mental state examination [MMSE], modified Boston naming test, and word list memory test), HDS-R, and DST were independently associated with ΔTSH after adjustment for age, education, depression, chronic illness, serum glucose, and serum vitamin B12. The increase TSH was associated with cognitive dysfunction in subjects with SCH.

Conclusion: In SCH, the decrease in thyroid function, rather than the thyroid function at a single time-point is a more important risk factor for the cognitive dysfunction in Korean elderly subjects. This result supports the need of thyroid hormone replacement in elderly subjects with SCH.

Nothing to Disclose: JHM, THK, THK, HC, SWC, KWK, YJP, KHY, KWK, DJP, HCJ

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