If you ask most physicians the effects of sub-optimal thyroid function on patients they will state that the most common symptoms are fatigue, weight gain, constipation and depression. Very rarely do we (doctors) discuss the benefits of thyroid on cardiovascular disease and cholesterol metabolism. However, there is a lot of data in the medical literature that shows thyroid hormone (specifically T3) reduces cholesterol, improves cardiac function and reduces your risks of cardiovascular disease. My goal of this blog is to make you aware that you can improve your cholesterol by doing more than just taking a “statin” drug.
Thyroid hormone is the driver of your metabolism. Simply explained, it effects the efficiency which every cell in the body utilizes carbohydrates, proteins, fats, vitamins and hormones. When you eat an apple for example, your body must break it down into simple sugars and those sugars are assimilated into the cell (in every organ) and converted to energy to do whatever the cell is supposed to do. So if it is a cardiac (heart) muscle cell it would influence how it contracts. Now think about the symptoms of low or sub-optimal thyroid: weight gain, fatigue, depression, constipation. It all starts to make sense when you realize the gut, brain, muscle etc do not utilize nutrients as efficiently as they should thus leading to these symptoms.
I want to focus on a few reasons why optimizing thyroid hormone is so good for your heart.
1. Thyroid hormone improves the clearance of LDL (low density lipoprotein or bad cholesterol) from the circulation. It does this by doing two things: The first is by increasing the expression or production of the LDL receptor which binds LDL cholesterol. The more efficiently the liver cells make this receptor the faster LDL is cleared from the blood. Secondly, it effects the production of an enzyme called HMG-CoA reductase which is the exact enzyme that drugs like zocor (simvastatin), lipitor and crestor target. Dr. Stanley Field and Dr. Richard Dickey studied and published this in the journal Preventive Cardiology in the Fall 2001.
What does this mean to you? I would say before your doctor decides to put you on a statin cholesterol lowering drug, ask him to make sure your free T3 is optimized to the upper limit of normal which is 4.0-4.4 in the blood.
2. It is the free T3 (triiodothyronine) that primarily affects the cells of the heart. T4 on the other hand has much less influence on cardiac function. It is for this reason that we want to focus on treating the free T3 when replacing thyroid hormone. Specifically, T3 increase the production of contractile proteins, calcium transfer proteins and other enzymes which increase both the rate and force of which the heart contracts. To put it in layman’s terms, T3 increases how hard and fast the heart beats, thus increasing its efficiency at pumping blood throughout the body.
3. T3 independently dilates the blood vessels and lowers what is referred to as systemic vascular resistance. This causes a decrease in blood pressure. Simultaneously, T3 stimulates the absorption of Na and water into the blood which increase the amount of blood that reaches the heart. This increase in blood volume coupled with increase force and rate of contraction with a reduction in the pressure equates to improved heart hemodynamics.
I recommend that you ask your doctor to do a complete thyroid workup at your next physical. Have him check the TSH, free T3, free T4, anti-thyroid antibodies and reverse T3. If the free T3 is sub-optimal and you have any symptoms the medical literature supports using Armour thyroid (or compounded dessicated thyroid) which is T4 + T3 to improve symptoms and cardiac function.