Hypothyroidism, Sex, and Age Predict Future Thromboembolic Events Among Younger People

Purpose: Aberrant thyroid function causes dysregulated metabolic homeostasis. Literature has demonstrated hypercoagulability in hypothyroidism, suggesting a risk for thromboembolic events (TEE). We hypothesize that individuals with hypothyroidism will experience more clinically-diagnosed TEE than euthyroid individuals.

Methods: De-identified patient data from the University of New Mexico Health Sciences Center were retrieved using thyrotropin (TSH; thyroid-stimulating hormone) for case-finding from 2005 to 2007 and ICD billing codes to identify TEE during the follow-up period of 10 to 12 years. Diagnoses affecting coagulation were excluded and 12 109 unique enrollees were categorized according to TSH concentration as Hyperthyroid (n = 510), Euthyroid (n = 9867), Subclinical Hypothyroid (n = 1405), or Overtly Hypothyroid (n = 327). Analysis with multiple logistic regression provided the odds of TEE while adjusting for covariates.

Results: There were 228 TEEs in the cohort over 5.1 ± 4.3 years of follow-up. Risk of TEE varied significantly across study groups while adjusting for sex, race/ethnicity, levothyroxine, oral contraceptive therapy, and visit status (outpatient vs non-outpatient), and this risk was modified by age. Overt Hypothyroidism conferred a significantly higher risk of TEE than Euthyroidism below age 35, and Hyperthyroidism conferred an increased risk for TEE at age 20. Analysis also demonstrated a higher age-controlled risk for a subsequent TEE in men compared with women (odds ratio [OR] = 1.36; 95% confidence interval [CI], 1.02-1.81). Subanalysis of smoking status (n = 5068, 86 TEE) demonstrated that smokers have 2.21-fold higher odds of TEE relative to nonsmokers (95% CI, 1.41-3.45).

Conclusions: In this retrospective cohort study, Overt Hypothyroidism conferred increased risk of TEE over the next decade for individuals younger than 35 years of age, as compared with Euthyroidism.