Subclinical thyroid disorders and cognitive performance among adolescents in the United States.
BACKGROUND
Thyroid hormone plays a crucial role in the growth and function of the central nervous system. The purpose of the study was to examine the relationships between the status of subclinical thyroid conditions and cognition among adolescents in the United States.


METHODS
Study sample included 1,327 adolescents 13 to 16 years old who participated in the Third National Health and Nutrition Examination Survey (NHANES III). Serum thyroxine (T4) and thyroid stimulating hormone (TSH) were measured and subclinical hypothyroidism, subclinical hyperthyroidism, and euthyroid groups were defined. Cognitive performance was assessed using the subscales of the Wide Range Achievement Test-Revised (WRAT-R) and the Wechsler Intelligence Scale for Children-Revised (WISC-R). The age-corrected scaled scores for arithmetic, reading, block design, and digit span were derived from the cognitive assessments.


RESULTS
Subclinical hypothyroidism was found in 1.7% and subclinical hyperthyroidism was found in 2.3% of the adolescents. Cognitive assessment scores on average tended to be lower in adolescents with subclinical hyperthyroidism and higher in those with subclinical hypothyroidism than the score for the euthyroid group. Adolescents with subclinical hypothyroidism had significantly better scores in block design and reading than the euthyroid subjects even after adjustment for a number of variables including sex, age, and family income level.


CONCLUSIONS
Subclinical hypothyroidism was associated with better performance in some areas of cognitive functions while subclinical hyperthyroidism could be a potential risk factor.
Wu
Tiejian
T
Department of Public Health, East Tennessee State University, Johnson City, TN 37614, USA. wut@etsu.edu
Flowers
Joanne W
JW
Tudiver
Fred
F
Wilson
Jim L
JL
Punyasavatsut
Natavut
N
D000293:Adolescent; D003071:Cognition / Q000502:physiology; D003072:Cognition Disorders / Q000097:blood / Q000453:epidemiology* / Q000209:etiology; D005260:Female; D006306:Health Surveys; D006801:Humans; D006980:Hyperthyroidism / Q000097:blood / Q000453:epidemiology / Q000523:psychology; D007037:Hypothyroidism / Q000097:blood / Q000453:epidemiology / Q000523:psychology; D007361:Intelligence Tests; D008297:Male; D015588:Observer Variation; D015995:Prevalence; D011581:Psychological Tests; D011932:Reading; D012307:Risk Factors; D012959:Socioeconomic Factors; D013037:Spatial Behavior; D013959:Thyroid Diseases / Q000097:blood / Q000453:epidemiology* / Q000523:psychology; D013963:Thyroid Hormones / Q000097:blood / Q000502:physiology; D014481:United States / Q000453:epidemiology
D013963:Thyroid Hormones