Effect of Metabolic Health on Severity of Thyroid Cancer: The Scripps Clinic Thyroid Cancer Cohort Analysis
Authors: Sharma Pranjali , Dhar Chirag , Levine Matthew Jason , McCallum James David , Martinez Renil Rodriguez 
Published: May 2021

Abstract
Introduction: The increasing prevalence of obesity has been linked to increased risk of cancers such as prostate, breast and endometrium, but its role in thyroid cancer is not clearly established. Since prevalence of obesity-related metabolic disturbances (dyslipidemia, dysglycemia) varies among individuals, it has been suggested that poor metabolic health, rather than obesity (defined by BMI), plays a role in thyroid cancer. We performed a retrospective review of our thyroid cancer cohort to evaluate the association between metabolic health and severity of thyroid cancer. Objectives: 1. Association between dyslipidemia and stages of thyroid cancer 2. Association between dysglycemia and stages of thyroid cancer. Methodology: The Scripps Clinic Thyroid Cancer Cohort includes 656 patients diagnosed with thyroid cancer from 2017-2020 in the Scripps Health System. IRB approval for our study was obtained in January 2020. Inclusion criteria: 1. Confirmed thyroid cancer on surgical pathology 2. First available lipid profile at least 6 months prior to diagnosis 3. First available HbA1c at least 6 months prior to diagnosis. A total of 214 patients with an available lipid profile were included in the analysis. Of those, 148 had an available HbA1c. Definitions used: 1. Dyslipidemia - total cholesterol &gt;=200 mg/dl or HDL &lt;40 mg/dl in males, &lt;50 mg/dl in females or triglycerides &gt;=150 mg/dl. 2. Dysglycemia - HbA1c &gt;=5.7%. Thyroid cancer stages were compared in patients with and without dyslipidemia and dysglycemia. Subgroup analysis was performed for patients above age of 55 years (n=103) due to difference in AJCC staging. Results: A larger proportion of dyslipidemic patients (28.4% vs 18.1%) had stage 2-4 thyroid cancer, but the difference was not statistically significant (p 0.07). A larger proportion of dysglycemic patients (36.3% vs 15.6%) had stage 2-4 thyroid cancer, a statistically significant difference (p 0.003). Similar findings were noted on subgroup analysis: a larger proportion of dyslipidemic (15.2% vs 8.2%) patients had Stage 3-4 thyroid cancer without statistical significance (p 0.1), while a statistically significant higher percentage of dysglycemic patients (20% vs 2.7%, p 0.01), had stage 3-4 thyroid cancer. A larger proportion of advanced thyroid cancer cases was noted in patients with both dyslipidemia and dysglycemia as compared to patients with only one abnormality or none. Conclusions: 1. Poor metabolic health, particularly dysglycemia, is associated with advanced stages of thyroid cancer, especially in the &gt;=55 years age group. Dysglycemia with dyslipidemia confers highest probability of advanced thyroid cancer. 2. Mechanisms by which dysglycemia affects thyroid cancer severity requires further rigorous study. 3. Based on our study, we recommend a thorough discussion regarding risk of advanced thyroid cancer in patients with poor metabolic health and thyroid nodules.