The thyroid is a small butterfly shaped gland located in your neck. Though it weighs only about an ounce, the thyroid gland has some very important functions to carry out that have a major impact on one’s health. It maintains body temperature, controls the rate of energy production (including oxygen use and basal metabolic rate), regulates the skeletal and muscular growth of children and heavily influences brain chemistry and thus brain function.
Additionally the thyroid gland has major influence in all of these areas:
Enhances a portion of the nervous system called the sympathetic nervous system.
Promotes breakdown of blood sugar, mobilizes fats, essential for protein synthesis, enhances the liver’s synthesis of cholesterol.
Promotes normal adult nervous system function and mood.
Promotes normal functioning of the heart.
Promotes normal muscular growth and function.
Promotes normal GI motility and tone; increases secretion of digestive juices, particularly that of the gallbladder and the stomach.
Promotes normal female reproductive ability and lactation.
Promotes normal hydration and secretory activity of the skin.
The thyroid gland takes iodine, which is found in many foods, and converts it into thyroid hormones thyroxine (T4) and triiodothyronine (T3). It is estimated that Iodine makes up about 0.00004% of total human body weight and iodine is found in highest concentration in the thyroid the gland cells. These cells combine iodine and the amino acid tyrosine and hydrogen peroxide (using an enzyme called thyroid peroxidase or TPO) to make the hormones T4 (thyroxin) and T3 (triiodotyrosine), which are then released into the blood stream and transported throughout the body attached to a protein called Thyroid Binding Globulin (TBG).
It is important to understand that T4 is inactive thyroid hormone and about 93% of the thyroid’s production of hormone is T4. Only about 7% of the hormone the thyroid gland produces is active thyroid hormone (T3). The 93% inactive T4 hormone must be converted to T3 in order for this active hormone to generate all the important effects in the body. 60% of T4 is converted to T3 in the liver and 20% is converted into another inactive thyroid hormone called reverse T3 (rT3). Another 20% of T4 is converted to T3 Sulfate (T3S) and triiodothyroacetic acid (T3AC) and is acted upon by the digestive tract bacteria (assuming your digestive tract is in healthy balance of bacteria) and fully converted to T3. Any remaining T4 hormone that wasn’t transformed into T3 or inactive T3 forms will be converted into T3 by the peripheral tissues (such as in brain cells, kidneys and muscle cells).
Only the active T3 hormone exerts is controlling effect on metabolism and all the other functions it governs or modulates. The thyroid is the master gland of your metabolism and so it has a very important job. People who suffer from thyroid malfunction experience many different kinds of health complications affecting a multitude of systems in their body. Every cell in your body had thyroid hormone receptor sites so that little gland affects the function of every cell in your body!
An estimated 27 million Americans suffer from thyroid dysfunction, half of which go undiagnosed. Women are at a and estimated 24 times greater risk of developing thyroid malfunction and this risk increases with age and also for those who have thyroid dysfunction within their family.
When the thyroid gland begins to malfunction many doctors neglect to ask the very important question of why. Adrenal problems, hormonal imbalances, poor blood sugar metabolism, irregular immune function and gut infections are all signals that the thyroid might be depressed.
Many times replacement hormones are used in an effort to wipe out symptoms without understanding what has caused the thyroid to malfunction in the fist place. More often than not the relief these drugs provide is short-lived, or never really works, because in order to really address the health of the very important thyroid gland, the systems of the entire body must be taken into account. So even though you are taking medications for thyroid dysfunction you may still have problems with your thyroid (even though your TSH levels are in the normal range). For example you can have problems with how the thyroid hormones are transported or how inactive T4 hormone is converted to active T3 hormone. You may have issues with the end effect the thyroid hormone is intended to have at the cell level.
Here is a List of The Influences of Thyroid Hormones on Physiological and Metabolic Function
Bone: Deficiency of thyroid hormones lead to a decrease in bone development and an abnormal architecture of the bone that is created. Generally, a functionally low (which means low but not flagged as of yet) serum calcium is noted in hypothyroidism. Elevated thyroid hormones causes an increased serum calcium, as it pulls calcium from the bone, leading to increased risk of pathological fractures of the spine and weight-bearing joints.
Gastrointestinal Function: Transit time is affected directly by thyroid hormones as is absorption of nutrients.
Male Hormones: Hypothyroidism has been linked to diminished libido and impotence. Although this condition is more rare in men, it must be considered in treating these conditions.
Liver and Gallbladder Function: Low thyroid function caused decreased liver clearance and gall bladder congestion through thickening of the bile, often also associated with an elevation of cholesterol. Unfortunately, also often treated with cholesterol lowering drugs while the thyroid function is the cause of the elevated cholesterol.
Body Composition: As you may know all too well, low thyroid function causes an inability to lose weight. This is caused by a slowed conversion of glucose and fat into energy, and altering the way Human Growth Hormone (HGH) is metabolized in the body.
Blood Sugar Regulation: Low thyroid slows the insulin response to glucose following eating carbohydrates or sugar and it also slows glucose uptake into cells and tissues, and slows absorption of glucose from the intestinal tract. In other words, your entire energy production system is slowed. It is quite confounding to your body and brain, in that the glucose is in the blood, but the tissues are not able to absorb it. This really confuses the pituitary gland and adrenal glands, resulting in a “stress physiology,” even if life is good.
Cholesterol: As mentioned earlier, low thyroid increases your cholesterol and triglycerides, so your doctor tells you your diet is poor. You become even more strict in your diet, and the tissue starvation (low glucose, low energy) gets worse, which makes the stress physiology worse, which makes your cholesterol higher, which prompts your doctor to put you on cholesterol medication, which interferes with energy production, which further stresses your physiology…whew! You are frustrated!
Depression: Low thyroid impairs the production of stimulating neurotransmitters, which are the chemicals that antidepressants work on. Low stimulating neurotransmitters leaves you, as one of my professors described, feeling “lower than a snakes belly.”
Female Hormones: Low thyroid changes the way estrogen is metabolized in the body, shifting toward an estrogen metabolite that has been proven to increase the risk of breast cancer.
Stress: Low thyroid slows the elimination of the stress hormone cortisol, which leaves you feeling stressed out, not because of “stress,” but because the stress hormone can’t be removed efficiently.
Detoxification: Low thyroid slows an enzyme critical for metabolic biotransformation, or detoxification, the process by which the body binds and removes all environmental chemicals, and normal byproducts of metabolism, including hormones. “Toxicity” further slows your metabolism, and leads to headaches and other toxic symptoms.
Digestion: Low thyroid reduces the release of Gastrin, which determines the output of hydrochloric acid in the stomach, leading to poor protein digestion, sour stomach, and GERD.
Thermoregulation: Regulation of body temperature is affected by low thyroid, resulting in hot flashes and night sweats, which is especially prominent in perimenopausal women. This is often blamed on estrogen dropping, but may be directly caused by low thyroid.
PMS and Infertility: Low thyroid affects the progesterone receptors, making them less sensitive to progesterone, which feels like low progesterone, although the progesterone levels may be normal. Since the activity of progesterone is diminished, the health of the uterus is insufficient for implantation in the second half of the female cycle, leading to difficulties getting pregnant and PMS. Low thyroid also reduces sex hormone binding proteins, leading to an increase in estrogen activity.
Anemia: Low thyroid, as mentioned affects protein metabolism, which then lowers the red blood cell mass, which carries oxygen to tissues for metabolism of energy. Yes, another mechanism for feeling lousy.
Homocysteine: Low thyroid slows a process called methylation, often evidenced by elevated serum levels of homocysteine. Elevated homocysteine in the blood has been proven as a risk factor for cardiovascular disease, Alzheimer’s and other neurodegenerative disorders, and cervical dysplasia.
Due to the effect the thyroid hormones have on so many systems of the body, including metabolism and nervous system function, a minimum of two mechanisms can lead to sleep apnea. Number one is the weight gain that typically occurs about the face and often, an enlarged thyroid gland, which can physically impede airflow through the airway, leading to sleep apnea. In addition the reduction in proper thyroid hormone leads to impairment of the part of the brain stem that is in charge of the cardio-respiratory centers, thus leading to abnormal breathing patterns during sleep. Weakened respiratory muscles due to hypothyroid myopathy can be a third cause for sleep apnea.