Cardiometabolic Health and The Thyroid

Cardiometabolic health is often an overlooked aspect in the management of hormonal health and, specifically, thyroid health. The two are intricately connected, displaying a complex, weblike relationship that is both interdependent and bidirectional. 

Many are aware of the connections between the thyroid and atherosclerosis (the buildup of fats, cholesterol and other substances in and on artery walls, commonly known as plaque), hyperlipidemia (an abnormally high concentration of fats or lipids in the blood) in patients with hypothyroidism and atrial fibrillation in hyperthyroidism. However, the connection reaches much further, and what is often overlooked is the impact of cardiovascular disease on the thyroid by the processes of oxidative stress and inflammation. So, the implications are more complicated and circular than once believed. 

Oxidative Stress and Inflammation

Inflammation and oxidative stress, produced by adipose tissue, an antioxidant-poor diet, inflammatory diet, and environmental stressors, have a negative impact on the thyroid. Both hyperthyroid and hypothyroid disease is associated with increased oxidative stress. It is my belief that inflammation and oxidative stress are often disregarded in patients with thyroid disease, especially in those who continue to struggle with symptoms despite receiving treatment. 

Insulin Resistance, Diabetes and Glucose

The connection between the endocrine system and cardiovascular disease is something physicians see frequently in patients with insulin resistance and diabetes. What many don’t know is that by improving glucose control, we can improve thyroid hormone profiles and function. Additionally, research shows that individuals with increased insulin (resistance) have a higher incidence of thyroid nodules, larger thyroid volume and a higher incidence of thyroid cancer, which seems to be somewhat mitigated by using Metformin, a drug prescribed to control high blood sugar in patients with type 2 diabetes.  

Cholesterol, Hypertension and Cardiovascular Disease

Thyroid disease is a risk factor for cardiometabolic disease. Even patients who are considered “euthyroid” or “normal,” but have positive autoimmune antibodies, are found to have been at an increased risk for cardiovascular disease. Both hypo and hyper thyroid states have noted associations with cardiac disease, and there is an intimate connection between the heart and the thyroid, which are linked embryologically. Unfortunately, what is rarely discussed with patients is the impact of thyroid hormones on virtually every physiologic, anatomic component of the entire cardiovascular system, including the blood vessels. 

For those with thyroid disease or cardiovascular disease, it is important that we remain mindful of the interconnectedness of these conditions and we do not treat them in isolation.

Worth Reading

Azar, Sami T., Hage, Mirella, Zantout, Mira S., Thyroid Disorders and Diabetes Mellitus, PMC/2011

Chao, Liu, Chen, Guofang, Derwahl, Michael, et al., Metformin and thyroid disease, Journal of Endocrinology/2017

Duan, Yan, Fu, Jing, Liu, Jia, et al., Association Between Thyroid Hormones, Thyroid Antibodies, and Cardiometabolic Factors in Non-Obese Individuals With Normal Thyroid Function, Frontiers in Endocrinology/2018

Gao, Ling, Lu, Ming, Yang, Chong-Bo, et al., Mechanism of subclinical hypothyroidism accelerating endothelial dysfunction, Spandidos Publications/2014

Grais, Ira Martin, Sowers, James R., Thyroid and the Heart, PMC/2014

Monostra, Michael, Metabolic management restores thyroid function in adults with type 2 diabetes, Healio/2020