Thyroid Function Explained - Part 3


The thyroid gland, with the help of the pituitary, is the most important organ in the body for controlling weight and body fat. Thyroid hormones define the rate of cellular metabolism. If the thyroid gland is functioning properly, and enough thyroid hormone is getting to the cells, the energy from food is properly utilized. If there is a problem with the gland itself or if something is interfering with the thyroid hormone's ability to bind to it's target cells, metabolism alters, slowing down or speeding up every process in the body, which in turn can cause many reccuring problems.


Fatigue can be directly related to problems with the thyroid. The process by which energy from food is released and transferred to useable energy by the cells is a complex chain of chemical reactions known as cellular respiration. Some energy is released from food in the absence of oxygen (anaerobic respiration), but most is derived in the mitochondria of the cells in the presence of oxygen (aerobic respiration). In the mitochondria, aerobic respiration produces cellular energy in the form of ATP ( a large energy molecule). T3 and T4 are needed to utilize oxygen during aerobic respiration. If T4 or T3 levels are low, cellular respiration and energy are depleted, excess oxygen builds up in the cells, and oxidative, or free-radical, damage occurs. When these levels are low, the number of mitochondria in our cells actually begins to decrease.


The metabolism of fats and absorption of essential fatty acids (EFAs) are important functions of the thyroid. Insufficient T4 to stimulate fat metabolism can lead to Hyperlipidemia, or elevated cholesterol. Whithout the benefit of cardioprotective nutrients from essential fatty acids, you may be at an increased risk of cardiovascular disease. If you have a high cholesterol reading, be sure to have your thyroid function evaluated before beginning medication. T3 is necessary for the utilization of oxygen by the mitochondria during cellular respiration. Inadequate T3 in the cells has a negative effect on oxygen consumption. Excess oxygen results in an increase in the oxidation of lipids (fats) and free radical damage. Increased oxidation of the low-density lipoprotein (LDL) form of cholesterol, often reffered to as "bad" cholesterol, has been identified in hyperthyroidism and hypothyroid states.


T4 also influences how quickly glucose (sugar) is absorbed from the intestines and then taken up by the cells. T4 stimulates the conversion of proteins and fats to glycogen when blood sugar is high and the transformation of glycogen to glucose when blood sugar is low. The thyroid gland assists the pancreas and liver in maintaining stable blood sugar. In other words, T4 increases insulin response.


Chronic stress affects the thyroid and endocrine function in a number of ways. The pituitary gland, the bodies "master gland," stimulates and controls the function of the adrenal cortex by secreting adrenocorticotropic (ACTH). If required to maintain a constant level of the major stress hormone cortisol in response to stress, the pituitary gland may over work. Too much production of ACTH may divert the pituitary from manufacturing other tropic hormones such as TSH, FSH, and LH. Cortisol production requires tyrosine, the same amino acid needed for the synthesis of T4. Excess cortisol production can deplete tyrosine levels, making it unavailable to the thyroid gland to make thyroid hormones. Stress depletes other important nutrients for T4 production, namely chromium and zinc. Excessive cortisol production from chronic stress also inhibits the conversion of T4 to T3 and the secretion of TSH.



behavior and mood...depression, fatigue, sleepiness, poor concentration
cardiovascular.........slow pulse rate (<70bpm):
cholesterol..............elevated cholesterol
features..................coarse voice, stunted growth, enlarged thyroid
Gastrointestinal........slowed digestion, bloating, heartburn, poor appetite
metabolism..............decreased basal metabolic rate, weight gain
muscles and reflexes..muscle aches, cramping, numbness in hads and feet
respiratory...............breathing slows, poor ventilation
Tolerance to temp..... intolerance to cold.


behavior and mood...nervousness, irritability, insomnia, exhaustion
cardiovascular.........heart palpitations, rapid pulse
cholesterol..............decreased cholesterol
features.................bulging eyes, enlarged thyroid
gastrointestinal........diarea, increased appetite
metabolism..............increased basal metabolic rate, weight loss
muscles and reflexes..muscle weakness, tremors
tolerance to temp.....intolerance to heat.

I know that's alot to stomach, but perhaps people will consider the importance of their thyroid gland before taking thyroid meds out of ignorance or being miss informed...the choice is ultimately and save!