Abstract P374: Thyroid-stimulating Hormone Levels and Coronary Artery Calcium Score. The Brazilian Longitudinal Study of Adult Health (ELSA-Brasil)
Authors: Peixoto-Miranda Erique J , Bittencourt Marcio S , Staniak Henrique L , Pereira Alexandre C , Foppa Murilo , Santos Itamar S , Lotufo Paulo A , Bensenor Isabela M 
Published: March 2022

Introduction:
There is scarce information about the association between thyroid stimulating hormone (TSH) levels with subclinical atherosclerosis as the coronary artery calcium score (CAC).

Hypothesis:
we assessed the hypothesis that the extremes quintiles of TSH were associated with high values of CAC.

Methods:
We analyzed cross-sectionally baseline data of the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil), a cohort of civil servants aged 35-74 years-old, in 4549 participants with CAC information. We excluded individuals using medications that affect thyroid function, with overt thyroid disorders and who self-reported cardiovascular disease. We included in the analysis TSH levels of subjects with euthyroidism and with subclinical thyroid disorders (subclinical hypothyroidism and hyperthyroidism). Logistic regression models evaluated increasing quintiles of TSH as the independent variables and CAC greater than 100 Agatston units as the dependent variable. Multivariate models were adjusted for age (continuous), sex, race (white, mixed, black, Asian, indigenous), body-mass index (continuous), hypertension (yes/no), diabetes (yes/no), dyslipidemia(yes/no), smoking (never/former/current), glomerular filtration rate (continuous, CKD-Epi formula) and C-Reactive Protein (log transformed).

Results:
From 3,836 subjects included (median age = 49 years;52.1%, women), 3,551 (92.6%) had euthyroidism, 239 (6.2%) subclinical hypothyroidism, and 46 (1.2%) subclinical hyperthyroidism. Frequencies of women, whites, never smokers, overweight/obesity and of reduced glomerular filtration rate increased according to TSH quintiles, but the frequency of diabetes decreased. Quintiles of TSH were from 1
st
to 5
th
respectively: TSH:0-0.99; 1.00-1.38; 1.39-1.85 (reference); 1.86-2.67; and 2.68-35.5 mIU/L. Using the 3
rd
quintile as reference, the odds ratio OR (95% Confidence Interval) for CAC greater than 100 Agatston units were 1.57 (1.05-2.35) for the 1
st
; 0.95 (0.62-1.46) for the 2
nd
; 1.25 (0.81-1.87) for the 4
th
; and 1.18 (0.77-1.80) for the 5
th
quintiles. Restricting analysis to the 3,551 euthyroid participants, quintiles of TSH in normal range were from 1
st
to 5
th
respectively: 0.40-0.99; 1.00-1.35; 1.36-1.75 (reference); 1.76-2.43 and 2.44-4.0. Using 3
rd
quintile as reference, we also observed a significant association of the 1
st
quintile with CAC: 1.70 (1.11-2.59) but not with 2
nd
0.95 (0.60-1.50), 4
th
1.46 (0.95-1.70) or 5
th
1.08 (0.69-1.70) quintiles.

Conclusion:
contrasting with previous studies that did not find any association between subclinical hypothyroidism and prevalent CAC, our results point to an association of low and low-normal TSH levels with prevalent CAC. Although one previous study showed an association between low normal TSH levels with CAC, our results also extended this association to low TSH levels.