It is estimated that approximately 20 million Americans have a thyroid disorder which means 1 in every 10 people. Hypothyroidism is caused from decreased production of thyroid hormone which results in decreased metabolism. Hypothyroidism occurs more commonly in women 1.2-2% as compared to men 0.2 %. Hypothyroidism is also more common in menopausal women. People at high risk for thyroid dysfunction include post-partum women, people with high levels of radiation exposure (< 20mGy), elderly, and people with Down Syndrome. The elderly are often undiagnosed because symptoms mimic aging6. Also as a person ages, the incidence increases.
The primary cause of hypothyroidism is the failure of the thyroid gland termed primary hypothyroidism. There are several causes of primary hypothyroidism such as Hashimoto’s disease (inflammation of the thyroid by an autoimmune mechanism), iatrogenic hypothyroidism such as after radioactive iodine therapy, iodine deficiency, enzyme defects, underdevelopment of the thyroid gland, and substances that cause goiters. Another cause of thyroid disorder is Wilson’s Syndrome. A less common cause of hypothyroidism is from pituitary or hypothalamic disease called secondary hypothyroidism. This article will focus primarily on the role of the thyroid hormones, symptoms, and treatment of hypothyroidism, with additional information on Wilson’s Syndrome.
The thyroid is a gland in the body which is composed of two lobes on either side of the trachea2. The thyroid produces hormones that are involved in almost every part of the body. In adults, the major role is to maintain metabolic stability. Thyroid hormones are stored in the thyroid gland and in the blood. The hypothalamic-pituitary-thyroid axis is designed to monitor levels of the hormones in the body and to maintain levels in a very specific narrow range.
The synthesis of thyroid hormone occurs when the thyroid hormones thyroxine (T4) and triiodothyronine (T3), the more biologically active hormone, are formed on thyroglobulin. The thyroid cell is the site where the synthesis of the large glycoprotein thyroglobulin takes place. Iodinated tyrosine, which is present in the glycoprotein, binds together to make the active thyroid hormones. Iodine is an important element for the functioning of the thyroid gland and an adequate supply is needed.
Three proteins are involved in the transport of T4 and T3: thyroid-binding globulin (TBG), thyroid-binding prealbumin (TBPA) and albumin. The secretion of T4 occurs primarily in the thyroid although this is not the case for T3. T3 is formed from the breakdown of T4 in the peripheral tissues. In comparing the two hormones, T3 is the more active, therefore T3 plays the primary role in regulating metabolic activity within the body. The thyroid’s growth and function is maintained by TSH (thyroid stimulating hormone). The thyroid is regulated by several mechanisms. First the anterior pituitary gland secretes TSH which regulates the thyroid hormones. Also the process of removing iodine from T4 and T3 is regulated by many factors which include nutrition, drugs, illness, and other non-thyroid hormones. <http://www.project-aware.org/Resource/articlearchives/thyroid.shtml>
In Wilson’s syndrome there is a problem converting T4 to T3. In normal thyroid function, T4 converts to T3 in the active form and reverse T3 (RT3) in an inactive form. The enzyme that is used to convert T4 to T3 is inhibited by stress, acute and chronic illness, fasting and the stress hormone cortisol. In times of stress, the body produces more T4 to RT3 to conserve energy for stress. A vicious cycle then occurs with more RT3 than T3 being produced.
Wilson's Syndrome symptoms :
In Wilson’s Syndrome, the thyroid levels appear normal although the patient is still experiencing symptoms of low thyroid. These symptoms worsen in periods of physical or emotional stress. Possible stressors include childbirth, surgery, divorce, death in family, or job and family stress. The symptoms persist even when the stressors have passed.
Nonpharmacologic treatment includes getting plenty of rest, eliminating as much emotional stress as possible, moderate exercise for stress control, and eating a well balanced diet. Pharmacologic treatment includes reducing T4 by giving T3. In this fashion, the body senses it has enough hormones and decreases production of T4, which decreases production of RT3. Treatment only lasts for a couple of weeks or months. Sustained release T3 seems to be best tolerated in twice daily dosing. Immediate release T3 is marketed under liothyronine (Cytomel), but does not appear to work as well as sustained release T3, which a compounding pharmacy would have to prepare. Dessicated thyroid (Armour thyroid) has also been used since its main constituent is T3 although it has T4 as well. Levothyroxine (Synthoid) is not as good of an option because it is only T4.
Decreased levels of thyroid hormone result in swelling around the eyes and decreased heart rate. A patient’s speech is often slow and the voice is hoarse. Also decreased reflexes are also common. In the later stages, there is accumulation of glycoaminoglycans into interstitial tissues and this accumulation results in edema of skin, muscle, heart, and striated muscles, which results in symptoms of a round puffy face, loss of hair and dry skin. Patients also can experience hearing loss, numbness in the extremities, and day time sleepiness. There is also a decrease in the conversion of carotene to vitamin A which causes the skin to have a yellowish color. Also hypothyroidism is involved in decreased conversion of estrogen precursors into estrogen which can result in infertility.
Lab tests performed in diagnosing and monitoring primary hypothyroidism are serum TSH and Free Thyroxine Index (FT4I). The first step in evaluation is to measure serum TSH and free T4 index or serum free T4. Overt primary hypothyroidism reveals a rise in TSH and free serum T4 level is low. If the serum free T4 is low and the TSH is normal or low then diagnosis of central hypothyroidism or nonthyroidal disease can be made2. Additional tests might include free T4, thyroid autoantibodies such as antithyroglobulin autoantibodies and anti-thyroid peroxidase, and in the case of suspicious thyroid structure then a thyroid scan and/or ultrasonography. Less common but very important tests also include total T3 and free T3 as TSH is often normal indicating euthyroid despite adequate T3 levels which could be indicative of Wilson’s Syndrome.Contact Us Today