Your thyroid is a small, butterfly-shaped gland in the front of your neck, just below your Adam’s apple (larynx). Weighing less than one ounce, its two lobes span your windpipe (trachea). Its main function is to produce thyroid hormones that ultimately regulate the metabolism of carbohydrates, fats, and proteins, to produce energy. During this primary process, the thyroid gland also has an important role in the function of other organs and tissues in the body, including your heart, brain, liver, kidneys, muscles, and skin. Therefore, optimal functioning of your thyroid supports overall well-being.
How does the thyroid gland work?
Your thyroid gland is stimulated by a multi-step process. First, the hypothalamus in the brain produces thyrotropin-releasing hormone (TRH), which tells the anterior pituitary gland, located at the base of the brain, to produce and secrete thyroid-stimulating hormone (TSH). It is TSH that then stimulates the thyroid gland to produce thyroid hormones.
The primary function of the thyroid is to produce two hormones: triiodothyronine (T3) and prohormone thyroxine (T4), which both influence every cell in the body. Together, these two hormones regulate body temperature, metabolism, and heart rate. For this to happen, though, the essential element iodine must be present. Iodine is supplied from the diet because your body doesn’t make it. Iodine combines with the amino acid tyrosine to produce T3 and T4.
Production of T3 and T4 is part of a closed feedback loop, meaning when T3 and T4 are low, TRH stimulates the production of TSH to initiate production of more T3 and T4. When T3 and T4 are elevated in the blood, TRH is not made and doesn’t stimulate TSH, thus T3 and T4 can stabilize in the blood.
T3 is the active form of the two thyroid hormones. About 20 percent of T3 is secreted into the bloodstream directly from the thyroid. The other 80 percent of T3 is produced from the conversion of T4 in the kidneys and liver.
T4 is considered the inactive thyroid hormone. The typical thyroid produces about four times as much T4 as it does T3.
The thyroid gland also produces calcitonin, a hormone that regulates the amount of calcium and phosphate in your blood, opposing the action of parathyroid hormone (PTH) produced by the parathyroid gland located just behind the thyroid gland. Calcitonin decreases blood calcium levels by suppressing the resorption of bone by osteoclasts – cells that break down bone matrix to release calcium and phosphorus into the blood. This is a very tightly controlled process because blood calcium levels have a very narrow range of normal.
Signs your thyroid gland might not be functioning optimally
While some might not be aware that their thyroid is not functioning properly, others can notice a physical enlargement of the gland in their neck, otherwise referred to as a goiter. Over time, if your thyroid is under-functioning, you will likely begin to notice. Fatigue and weight gain are the classic signs, because you are not efficiently metabolizing your food into energy, so you have less energy to use. On the flip side, your thyroid can be over-working. You might notice unintentional weight loss, even with an increased appetite and over-consumption of calories. The other classic signs include rapid heartbeat, feelings of nervousness, sweating, thinning of hair, and difficulty sleeping. The remainder of this article focuses on issues associated with an under-active thyroid.
Signs and symptoms of an under-active thyroid
Thyroid issues can result in complications that affect other organs outside the thyroid gland. For example, high cholesterol levels – specifically LDL and total cholesterol – are common in individuals who have an under-active thyroid. Elevated cholesterol increases the risk for cardiovascular disease. An under-active thyroid gland can also affect nerve function, resulting in “brain fog” or problems with nerves in your extremities. Damage to these nerves can manifest as pain, numbness, and tingling in hands or feet (called peripheral neuropathy). Nerve damage can also cause muscle weakness or loss of muscle control. An under-functioning thyroid can also affect fertility or cause congenital disabilities in children from mothers with low thyroid.
Risk factors for under-active thyroid
You have an increased risk for an under-active thyroid if you are a female older than 50. Other risk factors include:
- A family history of thyroid disease or any autoimmune disease
- Personal history of type 1 diabetes, rheumatoid arthritis, or other autoimmune disorder
- History of taking anti-thyroid medications for hyperthyroidism
- Past thyroid surgery
- Radiation to the neck or upper chest
What can you do to keep your thyroid healthy? Diet, exercise, and lifestyle are the best behavioral modifications you can control.
Iodine is found in iodized salt, dairy products, shrimp, tuna, seaweed, eggs, and prunes, thus providing support for normal T3 and T4 functioning in the thyroid. Iodine’s RDA is 150 mcg daily. Many multi-vitamin/mineral formulations contain some iodine.
Vitamin B12 from diet or supplementation should be considered. Research suggests 40 percent of people with an under-functioning thyroid are also vitamin B12 deficient.1 The best food sources of vitamin B12 are liver, shellfish, beef, and foods fortified with B12.
Selenium is necessary to convert T4 to T3. Because selenium has the potential to reduce thyroid function if a person is also iodine deficient, selenium and iodine might need to be taken together. Brazil nuts, eggs, and animal products all contain selenium, although Brazil nuts are the richest source.
Omega-3 fatty acids support the uptake of selenium by the thyroid gland.* Fish that are high in omega-3 fatty acids include anchovies, mackerel, sardines, trout, salmon, and herring.
Avoid BPA, which is best known for its use in plastic bottles and linings of canned foods. Research has found an inverse relationship between BPA exposure and thyroid hormone levels, meaning as BPA exposure goes up, blood levels of certain thyroid hormone levels go down.2
Use headphones instead of holding your cell phone up to your ear. The research is still inconclusive on whether or not electromagnetic fields emitted from cell phones can cause detrimental effects on thyroid function, but they might affect TSH levels in cases of excessive use.3 So go hands-free.
Low-intensity exercise – one hour daily is recommended. Researchers found that compared to a group who did not exercise, a group who got 60 minutes of regular physical exercise along with thyroxine replacement therapy improved thyroid function after three months.4
Yoga can help stabilize thyroid hormones. Researchers found that 90 days of yoga for 30 minutes daily significantly improved T4 levels in women who had high levels, and also improved quality of life indices.5 The movements and meditation might be linked to improved stress, too.
- Jabbar A, Yawar A, Waseem S, et al. Vitamin B12 deficiency common in primary hypothyroidism. J Pak Med Assoc 2008;58(5):258-261.
- Meeker J, Ferguson K. Relationship between urinary phthalate and bisphenol A concentrations and serum thyroid measures in U.S. adults and adolescents from the National Health and Nutrition Examination Survey (NHANES) 2007-2008. Environ Health Perspect 2011;119(10):1396-1402.
- Mortavazi S, Habib A, Ganj-Karami A, et al. Alterations in TSH and thyroid hormones following mobile phone use. Oman Med J 2009;24(4):274-278.
- Bansal A, Kaushik A, Singh C, et al. The effect of regular physical exercise on the thyroid function of treated hypothyroid patients: An interventional study at a tertiary care center in Bastar region of India. Arch Med Health Sci 2015;3(2):244.
- Maske U, Barnwal S. Effect of yogic practices on the level of thyroxine (T4) in the female patients of hyperthyroidism. Internat J Med Health Res 2016;2(8):69-72.