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The thyroid gland produces hormones which regulate the metabolism of every cell of the body. A deficiency of thyroid hormones can affect virtually all functions of the body. A deficiency of thyroid hormones generally occurs for two main reasons: 1) When too little thyroid hormones are being made by the thyroid, we usually refer to this condition as hypothyroidism, and 2) When an adequate thyroid hormones are being made, but they are not being recognized by some or all of the cells and organs of the body, thyroid hormone resistance.
Hypothyroidism
The inadequate production of thyroid hormones can occur for a number of reasons. These include:
- A lack of thyroid-stimulating hormone, or TSH. In certain situations the pituitary gland may not make an adequate amount of TSH. In such cases, the thyroid gland is not stimulated by the pituitary gland to make thyroid hormones.
- When there is defective manufacturing or synthesis of thyroid hormones. This can occur for a number of reason including nutritional deficiencies such as a deficiency of iodine or other essential nutrients in the diet
- It can occur because of inadequate conversion of Free T4 into Free T3. This occurs when an enzyme needed to convert Free T4 into Free T3 is not available to make this necessary conversion.
- It can occur when there has been some form of injury to the thyroid gland, either because of infection, autoimmune disease (Hashimoto disease), removal of the thyroid gland by surgery, radiation, and postpartum (post childbirth) injury.
There are three types of hypothyroidism: primary, secondary and subclinical hypothyroidism. These are discussed in greater detail below.
Primary Hypothyroidism
Primary hypothyroidism is said to occur when there is defective manufacturing (synthesis) of thyroid hormones. It is usually recognized by elevated Thyroid Stimulation Hormone (TSH) levels and low Free T3 and Free T4 levels when blood testing has been done. This complex includes most all of the types of hypothyroidism created by a specfic defect of the thyroid gland itself.
Secondary Hypothyroidism
Secondary hypothyroidism occurs when TSH levels and thyroid hormone levels are low, yet the thyroid hormones which are being made are being made normally and they are normal thyroid hormones. In this case, the problem is in the pituitary gland as it is not acting to make sufficient TSH or the TSH it makes is not made well or sufficiently effective to stimulate production of thyroid hormones. Because of this blood test show low TSH levels and low thyroid hormone levels. In this situation, both the thyroid gland and the thyroid hormones made are perfectly normal and effective. The defect here is that TSH stimulation from the pituitary gland is inadequate, and, not enough thyroid hormone is being made.
Subclinical Hypothyroidism
Subclinical hypothyroidism occurs when there is elevated TSH levels while the thyroid hormone levels are normal. Here the body accommodates to decreased thyroid function by stimulating the pituitary to produce more TSH. This stimulates the thyroid to make more thyroid hormones, but still the amount of thyroid hormone being made is too low. This situation generally occurs when there has been a mild destruction or injury to the thyroid gland due to an autoimmune reaction. It also may occur as a reaction to certain drugs, trauma or surgery. It may also be do to a deficiency of the enzyme need to convert Free T4 into the active thyroid component Free T3.
Thyroid Hormone Resistance or Cellular Hypothyroidism
In this situation there are normal blood levels of both TSH and thyroid hormones however, there is evidence of low thyroid functional activity. This is usually defined as a low basal body metabolism rate. This suggests that even with adequate amounts of thyroid hormones being made, the cells are unable to use this thyroid hormone effectively.
Functional Hypothyroidism
This occurs when certain thyroid functions are measured and found to be diminished. In this situation, the effect of the thyroid and its production of thyroid hormones is now measured in regards to its effect on the body rather than looking at blood tests. The most common function is the Basal or Resting Metabolic Rate or BMR and Basal Body Temperature (BBT). By measuring BBT upon awaking in the morning, one can evaluate the BMR and hence the body’s response to thyroid hormone treatment. This functional test shows a much larger rate of hypothyroidism than diagnostic blood testing. Since most physicians order blood tests to measure T4 function, and since the BMR is related to T3 functioning which is more important to the cells and cellular function, blood testing often does not pick up these hypothyroid people. This condition is often referred to as Wilson’s Syndrom and is generally associated with poor conversion of T4 into T3 within the body and within the cells of the body. This approach has a value because blood tests for T3 may be unreliable hence missing nearly 50% of individuals with hypothyroidism. This may be seen when there is reversal of the Free T3-to-Free T4 ratio. T3 is four times more hormonally active and therefore more T3 is required by the body than is T4.
Reverse T3 Dominance and Multiple Enzyme Dysfunction
Reverse triiodothyronine (also known as Reverse T3, or rT3) is a molecule which is an isomer of triiodothyronine (T3). It is derived from thyroxine (T4). rT3, unlike T3, does not stimulate thyroid hormone receptors. When rT3 binds to these receptors, it ultimately blocks the functioning of normal T3.
Under stress conditions, the adrenal glands produce an excess of cortisol, and cortisol inhibits the conversion of T4 into T3. This ends up shifting the conversion of T4 into T3 towards creating rT3. Consequently, there is a widespread shutdown in T3 binding across the body. This condition is termed Reverse T3 Dominance. This then causes body temperature to fall, it slows the action of many enzymes and leads to a clinical syndrome called Multiple Enzyme Dysfunction (MED). MED ultimately produces the effects seen as rT3 hypothyroidism. The ususal symptoms of MED are: fatigue, headache, migraine, PMS, irritability, fluid retention, anxiety and sometimes panic disorders.
What is the Prevalence of Hypothyroidism?
It has been estimated that the rate of hypothyroidism, based on the levels of thyroid hormones in the blood, is between 1% and 4% of the general populations. Some suffer from moderate symptoms, while others suffer from severe hypothyroidism. Most, however, go entirely undetected. Based on factors other than blood tests it has been estimated that at least 10% to 12% of the general population suffer hypothyroidism from many of the reasons listed above. Statistics tell us that the rate of hypothyroidism increases steadily with advancing age. Some researchers estimate that the rate of hyperthyroidism in the younger adult population could be as high as 25%, while the rate in over 65 years of age, seniors when added to the rate for all adults, may reach as high as 40%.
How is Hyperthyroidism Recognized?
As with any other medical conditions hypothyroidism can be recognized by its symptoms, physical findings and laboratory testing. 1) First of all, the symptoms usually bring the individual into the doctor’s office for evaluation, 2) The medical history and physical examination often demonstrate a number of subtle symptoms and signs such as weight gain, slow pulse, low body temperature. 3) Routine or specific blood testing maybe done showing high TSH, low Free T4 or better still low Free T3. 4) The doctor may put medical history, signs and symptoms together to crate a high index of suspicion that hypothyroidism exists. While the symptoms of hypothyroidism alone are not always helpful, the key to making a good diagnosis is commonly found after eliminating all other medical conditions the laboratory findings and possibly most important of all, a trail of hormonal replacement therapy.
The main symptoms of hypothyroidism are:
- Depression
- Difficulty losing weight
- Dry skin
- Headaches
- Lethargy or fatigue
- Recurrent infections
- Sensitivity to cold
- Cardiovascular disease
- Loss of sex drive in men and women
- Muscle weakness and joint stiffness, pain and tenderness (similar to fibromyalgia)
- Hyperlipidemia (cholesterol and triglycerides)
- Memory problems, difficulty concentrating, forgetfulness
- Menstrual problems, infertility, miscarriage, premature delivery, stillbirths
- Constipation, shortness of breath, impaired kidney function
Physical Signs in Hypothyroid Disease:
- Goiter, a non symmetrical enlargement of the thyroid
- Symmetrically enlarged thyroid
- Decreased BMR by any method
- Decreased reflexes
- Physical findings which may or may not be due to hypothyroid disease: dry rough cool skin, superficial scales, brittle nails, course dry and brittle hair, hair loss, non-pitting edema (eyelids and hands), loss outer1/3 of eye brows, thickened tongue, constipation, shortness of breath, slow pulse rate, hearing impairment, peripheral neuropathies with tingling (paresthesias), carpal tunnel syndrome, muscular stiffness, weakness, obesity
Contributing Factors To Hypothyroid Disease
- Pregnancy, use of birth control pills or estrogen replacement, Tamoxifen for breast cancer
- Food allergies
- Celiac Disease (allergy or intolerance to wheat)
- Nutritional, vitamin, mineral deficiencies especially zinc deficiencies in elderly
Diagnostic Testing
- Decreased TSH, decreased Free T4 and/or decreased Free T3
- Abnormal rT3 test
- Elevated cholesterol and triglycerides
- Low blood sodium
- Anemia
- Increased homocysteine, C-reactive proteins, low HDL
- Impaired kidney function testing
If you have hypothyroidism, a good long-term relationship with a competent and caring physician, who can greatly help you. If you have questions, believe that your thyroid is not working correctly or that you have hypothyroidism, then call 760-320-4292 to make an appointment and get help.
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