The Thyroid and Autoimmunity Connection

The thyroid is a small, butterfly-shaped gland that is located in the anterior neck producing T3 (triiodothyronine) and T4 (tetraiodothyronine) hormones. These hormones affect every single tissue and regulate the body’s metabolism while being part of an intricate network called the endocrine system. The endocrine system is responsible for coordinating many of the body's activities. In the human body, the two major endocrine glands are the thyroid glands and the adrenal glands. The thyroid is controlled primarily by TSH (thyroid-stimulating hormone), which is secreted from the anterior pituitary gland in the brain. The anterior pituitary gland can stimulate or halt the secretion to the thyroid, which is a response only gland in the body.

Since the thyroid glands make T3 and T4, iodine can also help with the thyroid hormone production. The thyroid glands are the only ones that can absorb the iodine to help hormone growth. Without it, there can be complications like hyperthyroidism, hypothyroidism, and Hashimoto’s disease.

Thyroid Influences on The Body Systems

The thyroid can help metabolize the body, such as regulating heart rate, body temperature, blood pressure, and brain function. Many of the body’s cells have thyroid receptors that the thyroid hormones respond to. Here are the body systems that the thyroid helps out.

Cardiovascular System and the Thyroid

Under normal circumstances, the thyroid hormones help increase the blood flow, cardiac output, and heart rate in the cardiovascular system. The thyroid can influence the heart’s “excitement,” causing it to have an increasing demand for oxygen, therefore increasing the metabolites. When an individual is exercising; their energy, their metabolism, as well as their overall health, feels good.

The thyroid actually strengthens the heart muscle, while decreasing the external pressure because it relaxes the vascular smooth muscle. This results in a decrease of arterial resistance and diastolic blood pressure in the cardiovascular system.

When there is an excess amount of thyroid hormone, it can increase the heart’s pulse pressure. Not only that, the heart rate is highly sensitive to an increase or decrease in the thyroid hormones. There are a few related cardiovascular conditions listed below that can be the result of an increased or decreased thyroid hormone.

• Metabolic Syndrome
• Hypertension
• Hypotension
• Anemia
• Arteriosclerosis

Interestingly, iron deficiency can slow the thyroid hormones as well as increase the production of the hormones causing problems in the cardiovascular system.

The Gastrointestinal System and the Thyroid

The thyroid helps the GI system by stimulating carbohydrate metabolism and fat metabolism. This means that there will be an increase in glucose, glycolysis, and gluconeogenesis as well as an increased absorption from the GI tract along with an increase in insulin secretion. This is done with an increased enzyme production from the thyroid hormone, acting on the nucleus of our cells.

The thyroid can increase the basal metabolic rate by helping it increase the speed of breaking down, absorbing, and the assimilation of the nutrients we eat and eliminate waste. The thyroid hormone can also increase the need for vitamins for the body. If the thyroid is going to regulate our cell metabolism, there has to be an increased need for vitamin cofactors because the body needs the vitamins to make it function properly.

Some conditions can be impacted by thyroid function, and coincidentally can cause thyroid dysfunction.

• Abnormal cholesterol metabolism
• Overweight/underweight
• Vitamin deficiency
• Constipation/diarrhea

Sex Hormones and the Thyroid

The thyroid hormones have a direct impact on ovaries and an indirect impact on SHBG (sex hormone-binding globulin), prolactin, and gonadotropin-releasing hormone secretion. Women are dramatically more affected by thyroid conditions than men due to hormones and pregnancy. There is also another contributing factor that women share, their iodine vitals and their thyroid hormones through the ovaries and the breast tissue in their bodies. The thyroid can even have either a cause or contribution to pregnancy conditions like:

• Precocious puberty
• Menstrual issues
• Fertility issues
• Abnormal hormone levels

HPA Axis and the Thyroid

The HPA axis (Hypothalamic-Pituitary-Adrenal Axis) modulates the stress response in the body. When that happens, the hypothalamus releases the corticotropin-releasing hormone, it triggers the ACH (acetylcholine hormone) and the ACTH (adrenocorticotropic hormone) to act on the adrenal gland to release cortisol. Cortisol is a stress hormone that can lower inflammation and increase carbohydrate metabolism in the body. It can also trigger a cascade of “alarm chemicals” like epinephrine and norepinephrine (fight or flight response). If there is an absence of lowered cortisol, then the body will desensitize for the cortisol and the stress response, which is a good thing.

When there is a higher level of cortisol in the body, it will decrease the thyroid function by lowering the conversion of the T4 hormone to T3 hormone by impairing the deiodinase enzymes. When this happens, the body will have a less functional thyroid hormone concentration, since the body can’t tell the difference of a hectic day at work or running away from something scary, it can either be very good or horrible.

Thyroid Problems in the Body

The thyroid can produce either too much or not enough hormones in the body, causing health problems. Down below are the most commonly known thyroid problems that will affect the thyroid in the body.

• Hyperthyroidism: This is when the thyroid is overactive, producing an excessive amount of hormones. It affects about 1% of women, but it’s less common for men to have it. It can lead to symptoms such as restlessness, bulging eyes, muscle weakness, thin skin, and anxiety.
• Hypothyroidism: This is the opposite of hyperthyroidism since it can’t produce enough hormones in the body. It is often caused by Hashimoto’s disease and can lead to dry skin, fatigue, memory problems, weight gain, and a slow heart rate.
• Hashimoto’s disease: This disease is also known as chronic lymphocytic thyroiditis. It affects about 14 million Americans and can occur in middle-aged women. This disease develops when the body’s immune system mistakenly attacks and slowly destroys the thyroid gland and its ability to produce hormones. Some of the symptoms that Hashimoto’s disease causes are a pale, puffy face, fatigue, enlarged thyroid, dry skin, and depression.

Conclusion

The thyroid is a butterfly-shaped gland located in the anterior neck that produces hormones that help function the entire body. When it doesn’t work correctly, it can either create an excessive amount or decrease the number of hormones. This causes the human body to develop diseases that can be long term.

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References:

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Clinic Staff, Mayo. “Hypothyroidism (Underactive Thyroid).” Mayo Clinic, Mayo Foundation for Medical Education and Research, 4 Dec. 2018, www.mayoclinic.org/diseases-conditions/hypothyroidism/symptoms-causes/syc-20350284.

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