Hypothyroidism is caused by the lack of supply or response to thyroid hormones in the body. Hypothyroidism is the most prevalent endocrine system problem and it affects millions of individuals around the world. People with hypothyroidism typically suffer from fatigue, lack of energy, cold intoler
ance, weight gain, constipation, and dry skin.
Hypothyroidism occurs to a much higher extent than previously thought.
The National Health and Nutrition Examination Survey (NHANES III) concluded that 9.2% of the population had clinically significant thyroid disease. This was based on biochemical data obtained from a sample of 17,353 participants. That number includes both hyperthyroid and hypothyroid patients. However, it should be noted that hyper thyroid patients frequently end up as hypothyroid patients after ablation therapy. It has also been estimated that 20 million Americans have some form of thyroid disease and that up to 60% of these individuals are unaware of their condition. It was also noted that women are 5-8 times more likely to have thyroid problems compared to men.
Furthermore, studies also show that up to 75% of patients are not satisfied with their current treatment protocols. Considering the magnitude of hypothyroidism in the population, it is easy to see that it is a huge problem that has serious implications for healthcare systems.
Thyroid hormones regulate many key processes in the body. As a consequence of this, hypothyroidism may result in a constellation of clinical symptoms and signs.
The severity of these manifestations generally is reflective of the degree to which the thyroid is dysfunctional. It also reflects the time course of the development of hypothyroidism. Symptoms associated with hypothyroidism are often non-specific. These include weight gain, poor concentration, fatigue, diffuse muscle pain, depression, and menstrual irregularities.
There are symptoms that have a high specificity for hypothyroidism, and these include constipation, dry skin, cold intolerance, hair loss or thinning, and proximal muscle weakness.
The symptoms of hypothyroidism may vary with age and sex. Children and infants often present with failure to thrive. Women who have the disorder are often plagued with menstrual irregularities as well as infertility. In older patients, the sole manifestation may be cognitive decline.
Examination finding that is correlated with hypothyroidism includes delayed relaxation of deep tendon reflexes, goiter, dry skin, thin or brittle nails, and peripheral edema. Electrocardiograms performed on individuals with hypothyroidism reflect flattened T waves, bradycardia, and low voltage.
There are many reasons for hypothyroidism. The most common cause of hypothyroidism is the presence of autoimmune diseases. This affects people by the fact that the immune system cells mistake thyroid gland cells for pathogens. Therefore, the thyroid gland is destroyed in the process. This is more common in women compared to men.
The two most common autoimmune diseases are Hashimoto’s thyroiditis and atrophic thyroiditis.
Hypothyroidism can be classified according to primary, secondary, and tertiary forms. Primary hypothyroidism is due to abnormalities that are present in the thyroid gland itself. Secondary hypothyroidism is due to diseases of the pituitary gland, which decreases the production of TSH, while tertiary hypothyroidism is due to hypothalamic causes.
TSH, or thyroid-stimulating hormone, is the major hormone that stimulates thyroid hormone production. Due to the positive feedback from low levels of thyroid hormone, the concentration of TSH increases, and this characterizes primary hypothyroidism.
Sometimes, the thyroid gland does not fail completely, and thyroxine can be kept in the normal range. However, when the thyroid gland fails completely, the high levels of TSH are not enough to keep the thyroid hormone levels within normal range, resulting in overt secondary hypothyroidism.
Hashimoto’s thyroiditis is a hypothyroid condition. In this disease, the thyroid gland is enlarged to the infiltration of lymphocytes. The gland, upon palpation, is described as rubbery. Hypothyroidism is due to autoimmune damages to the cells of the thyroid gland, or thyrocytes. Typically, the titer of antibodies to thyroid antigen is elevated.
Surgical removal of all or part of the thyroid may also cause hypothyroidism.
This procedure is often done in patients who have hyperthyroidism. Some people with thyroid nodules, Graves’ disease, or thyroid cancer may need to have part of all of the thyroid removed.
Radiation treatment is another reason for hypothyroidism. Some people who have Graves’ disease, thyroid cancer, or nodular goiter may be treated with radioactive iodine.
The purpose of this is to destroy the thyroid gland. In addition, patients with Hodgkin’s disease, cancers of the head and neck, and lymphoma are often treated with radiation.
Untreated hypothyroidism is associated with a variety of serious health problems.
One of them is the increased risk of birth defects in infants born to untreated hypothyroid mothers. These infants may have significant physical and mental development issues since thyroid hormones are crucial for brain development.
Goiter is another complication. When the thyroid gland overt-exerts itself in order to produce more thyroid hormones, it may grow in size to the point that there may be a bulge in the neck. Goiters can also obstruct surrounding structures, such as the esophagus.
Cardiovascular problems are also associated with hypothyroidism.
Hypothyroidism increases the risk of heart disease because it increases the levels of LDL, which is unfavorable. Too much LDL can lead to atherosclerosis, hardening of the arteries, and increases the chances for a heart attack or a stroke.
Infertility is another common complication of hypothyroidism. When thyroid hormone levels are too low, it can inhibit ovulation, thereby reducing the chances that a woman can conceive.
Mental health issues are another problem. Mild hypothyroidism can cause depression. However, if left untreated, mild depression can escalate to more severe forms.
The risk factors for hypothyroidism have been well-established.
Gender is a risk factor- women are more likely to become hypothyroid compared to males. This disease affects only 0.1% of men, but it affects 1.5% of women. Age is another risk factor because hypothyroidism is more likely to develop after the age of 60.
People who have previously been treated with radioactive iodine are at an increased risk of hypothyroidism due to the fact that radiation also destroys the cells of the thyroid gland.
A family history of autoimmune diseases may also predispose a person to become hypothyroid. People who have a close relative with autoimmune diseases are at a high risk. People who have other autoimmune diseases are also at risk, such as type I diabetes and pernicious anemia.
Individuals who have had thyroid surgery in the past are also more likely to acquire hypothyroidism.
Girls and women who have Turner Syndrome, which occurs when there are more than two X chromosomes, are at an increased risk of hypothyroidism.
Down syndrome, or trisomy 21, is another genetic condition that may increase a person’s chances of becoming hypothyroid.
The diagnosis of primary hypothyroidism is confirmed by measuring the T4 and TSH levels. Hypothyroidism should be confirmed when the T4 count is low and the TSH level is high. When the TSH level is high, but the T4 count is low, then the condition is known as subclinical hypothyroidism. Most individuals who have subclinical hypothyroidism will go on to have clinical hypothyroidism or even overt thyroid failure. Triiodothyronine (T3) is not usually measured during laboratory examinations. This is because increased TSH levels stimulate the production of T3, which may lead to normal/high findings. However, in some varieties of hypothyroidism, the T3 count is also low.
Free hormone estimations are useful because they measure the active metabolites in the blood. It is also advantageous because it is not affected by conditions that either decrease or increase the levels of thyroid-binding proteins. The diagnosis of chronic autoimmune thyroiditis is, for the most part, clinical, but it should be supported by these findings: there should be high levels of anti-TPO antibodies, or there must be a biopsy finding of lymphocytic thyroiditis.
The majority of patients with hypothyroidism will require lifelong therapy. Both T4 and T3 can be used to treat hypothyroidism, however, since T3 has a short biologic half-life, T4 is used. Synthetic thyroxine preparations undergo de-iodination to become the biologically active form of T3. Synthetic thyroxine preparations are available as both generic and brand name in the United States. In 2004, the US Food and Drug Administration approved the use of generic thyroxine in place of brand name thyroxine. However, the American Association of Clinical Endocrinologists disregarded this ruling and concluded that generic forms of thyroxine are not bioequivalent to the brand name.
The dosing of thyroxine is typically 1.6 mcg per kg per day as an initial dose. In older patients, or those with cardiac diseases, the starting dose is 25 or 50 mcg, and this is increased b 25 mcg every 3-4 weeks until the full replacement dose is reached.
Pregnant patients should have their doses increased to 9 doses weekly at the first sign of pregnancy. Patients with subclinical hypothyroidism with a TSH level of less than 10 mlU/L should be given 50 mcg daily. This should then be increased to 25 mcg daily every 6 weeks until TSH levels decrease to the normal range.