Investigation of thyroid function and blood pressure in school-aged subjects without overt thyroid disease

This study was performed to ascertain whether a relationship exists between thyroid function and blood pressure in school-aged Chinese subjects without overt thyroid disease. A cross-sectional survey of 880 subjects (541 females and 339 males) aged 7–18 years in Bengbu, Anhui province was conducted. The investigation, which was based on a stratified random cluster sampling method, included a questionnaire and measurements of blood pressure, height, and body weight. Fasting blood samples were taken for measurements of thyroid-stimulating hormone (TSH), free 3,5,3′-triiodothyronine (FT 3 ) and free thyroxine (FT 4 ). Serum TSH and FT 3 were positively correlated with systolic and diastolic blood pressure Z scores (SBP-Z and DBP-Z) even after adjusting for body mass index (BMI) ( P < 0.05) but no correlation was observed between FT 4 and SBP-Z or DBP-Z after comparable adjustments ( P > 0.05). SBP-Z and DBP-Z in subjects with subclinical hypothyroidism were significant higher than in euthyroid subjects ( P < 0.05). Both SBP-Z and DBP-Z increased linearly with TSH concentration in boys after adjusting BMI ( P < 0.05); however, a similar linear trend was not observed in girls. Our findings support the hypothesis that elevated TSH and FT 3 concentrations increase blood pressure in school-aged Chinese subjects without overt thyroid disease; this increase may be even more significant in boys.