Hypothyroidism in detail - non-technical
Hypothyroidism is a condition in which a person’s thyroid gland is not producing enough hormone. It may be caused by an autoimmune disorder, a genetic defect in a newborn, certain medications, surgical removal of the thyroid gland, radiation therapy for cancer, and other reasons.
There are three main types of hypothyroidism. The most common is primary hypothyroidism, in which the thyroid doesn’t produce an adequate amount of T4. Secondary hypothyroidismdevelops when the pituitary gland does not release enough of the thyroid-stimulating hormone (TSH) that prompts the thyroid to manufacture T4. Tertiary hypothyroidism results from a malfunction of the hypothalamus, the part of the brain that controls the endocrine system. Drug-induced hypothyroidism, an adverse reaction to medication, occurs in 2 of every 10,000 people, but rarely causes severe hypothyroidism.
According to the National Institute of Diabetes andDigestive andKidneyDiseases (NIDDK), between 3 and 5% of the general population in the United States and Canada has some form of hypothyroidism. Apart from cretinism, which affects one child in every 3,000– 4,000, hypothyroidismis largely a disease of adults. The most common form of primary hypothyroidism in NorthAmerica is Hashimoto’s disease, an autoimmune disorder that is diagnosed in about 14 women out of every 1000 and 1 man in every 2000.
Caucasians and Hispanics (particularly Mexican Americans) in North America have higher rates of hypothyroidism than African Americans. The reason for this difference was not known as of 2009. Internationally, however, the most common cause of hypothyroidism is a lack of iodine in the diet. The prevalence of hypothyroidism caused by iodine deficiency in developing countries is 2–5%, increasing to 15% by age 75.
Hypothyroidism is an endocrine disorder; that is, it is caused by underfunctioning of a gland that is part of the endocrine system—a group of small organs located throughout the body that regulate growth, metabolism, tissue function, and emotionalmood.The thyroid gland itself is a butterfly-shaped organ weighing between half an ounce and 1.5 ounces in adults that lies at the base of the throat below the Adam’s apple and above the collarbone. It takes its name from a Greek word meaning ‘‘shield.’’ The thyroid consists of two lobes about 2 inches in length (in adults) connected by a thin strip of tissue called the isthmus.
Hypothyroidism develops when the thyroid gland fails to produce or secrete as much thyroxine (T4) as the body needs. Because T4 regulates such essential functions as heart rate, digestion, physical growth, and mental development, an insufficient supply of this hormone can slow life-sustaining processes, damage organs and tissues in every part of the body, and lead to life-threatening complications.
Hypothyroidism is not easy to diagnose because its symptoms are found in a number of other diseases; it often comes on slowly; and it may produce few or no symptoms in younger adults. In general, hypothyroidism is characterized by a slowing down of both physical and mental activities.
Risk factors for hypothyroidism include:
- Sex. Women are at greater risk of hypothyroidism than men. The female/male ratio among adults is between 2:1 and 8:1, depending on the age group being studied.
- Age over 50. In one Massachusetts study, 6 percent of women over 60 and 2.5 percent of men over 60 were found to be hypothyroid.
- Race. According to the National Institutes of Health (NIH), the rates of hypothyroidism in the United States are highest among Caucasians (5.1 percent) and Hispanics (4.1 percent) and lowest among African Americans (1.7 percent).
- Obesity. Having a small body size at birth and low body mass index during childhood.
- Family history of autoimmune disease.
- Having Turner syndrome, a genetic disorder in which a girl is born with only one X chromosome instead of the normal two. Turner syndrome affects 1 in every 2500 girls.
Causes and symptoms
The most common causes of hypothyroidism are:
- Hashimoto’s disease. This is an autoimmune disorder in which the patient’s immune system attacks the thyroid gland, leading to tissue destruction.
- Treatment for hyperthyroidism. People who have been treated for an oversupply of thyroid hormone (hyperthyroidism) with radioactive iodine (iodine-131) may lose their ability to produce enough thyroid hormone.
- Surgery on the thyroid gland.
- Radiation therapy for the treatment of head or neck cancer.
- Medications. Lithium, given to treat some psychiatric disorders, and certain heart medications may affect the functioning of the thyroid gland. Other drugs known to suppress thyroid function include amiodarone, a heart medication; interferon alpha, given to treat cancer; and stavudine, a drug used to treat HIV infection.
- Pregnancy. As many as 10% of women may become hypothyroid in the first year after childbirth, particularly if they have diabetes.
- Viral infections. These can cause a short-term inflammation of the thyroid gland known as thyroiditis in some people.
- A tumor in the pituitary gland. The pituitary gland produces a hormone called thyroid-stimulating hormone or TSH. Low levels of TSH can lead to secondary hypothyroidism.
- Congenital. About 1 baby in every 3,000–4,000 is born with a defective thyroid gland or no gland at all.
- Too little iodine in the diet. This cause of hypothyroidism is most common in developing countries; it is rare in North America and Europe.
Not every patient with an underactive thyroid has the same symptoms or has them with the same severity. Common symptoms of hypothyroidism, however, include the following:
- Increased sensitivity to cold weather.
- Dry, itchy skin and a pale or yellowish complexion.
- Dry brittle hair that falls out easily and nails that break or split.
- Goiter (swelling in the front of the neck caused by thyroid enlargement).
- Hoarse voice and puffy facial skin.
- Unexplained weight gain of 10–20 pounds, most of which is fluid.
- Sore and aching muscles, most commonly in the shoulders and hips.
- In women, extra-long menstrual periods or unusually heavy bleeding.
- Weak leg muscles.
- Decreased sweating.
- Memory loss or difficulty concentrating.
- Slowed heart rate (less than 60 beats per minute) and lowered blood pressure.
Hypothyroidism in adults can be difficult to diagnose because many of its early symptoms are not unique to it. In addition, the symptoms typically come on gradually; the person may simply feel tired or less energetic than usual, or develop dry, itchy skin and brittle hair that falls out easily. Hypothyroidism is sometimes referred to as a ‘‘silent’’ disease precisely because the early symptoms may be so mild that no one realizes anything is wrong. The classic symptoms of hypothyroidism—sensitivity to cold, puffy complexion, decreased sweating, and coarse skin— may occur in only 60 percent of patients. In addition, the patient’s loss of energy and low mood may be misdiagnosed as a psychiatric disorder, most commonly major depression. It may take months to years before the person or their doctor begins to suspect a problem with the thyroid gland.
It’s important to see a doctor if any of these symptoms appear unexpectedly. People whose hypothyroidism remains undiagnosed and untreated may eventually develop myxedema. Symptoms of this rare but potentially deadly complication include enlarged tongue, swollen facial features, hoarseness, and physical and mental sluggishness.
Myxedema coma can cause unresponsiveness; irregular, shallow breathing; and a drop in blood pressure and body temperature. The onset of this medical emergency can be sudden in people who are elderly or have been ill, injured, or exposed to very cold temperatures; have recently had surgery; or use sedatives or antidepressants.Without immediate medical attention, myxedema coma can be fatal.
In the United States, newborn infants between 24 and 72 hours old are tested for congenital thyroid deficiency (cretinism) using a test that measures the levels of thyroxine in the infant’s blood. If the levels are low, the physician will likely repeat the blood test to confirm the diagnosis. The physician may take an x ray of the infant’s legs. In an infant with hypothyroidism, the ends of the bones have an immature appearance. Treatment within the first few months of life can prevent mental retardation and physical abnormalities.
Older children who develop hypothyroidism may suddenly stop growing. If the child was above average height before the disease occurred, he or she may now be short compared to other children of the same age. Therefore, the most important feature of hypothyroidism in a child is a decrease in the rate of growth in height. If the disease is recognized early and adequately treated, the child will grow at an accelerated rate until reaching the same growth percentile where the child measured before the onset of hypothyroidism. Diagnosis of hypothyroidism in school-age children is based on the patient’s observations, medical history, physical examination, and thyroid function tests.
The doctor may notice such signs of hypothyroidism during an office examination as dry skin, facial puffiness, a goiter in the neck, thin or brittle hair, poor muscle tone, pale complexion, and a slower than normal heart rate. As previously mentioned, however, it is possible for a person with hypothyroidism not to have these symptoms.
The diagnosis of hypothyroidism is usually made by tests of the patient’s thyroid function following a careful history of the patient’s symptoms. The first test is a blood test for thyroid-stimulating hormone, or TSH. TSH is a hormone produced by the pituitary gland in the brain that stimulates the thyroid gland to produce thyroid hormone. When the thyroid gland is not producing enough hormone, the pituitary gland secretes more TSH; thus a high level of TSH in the blood indicates that the thyroid gland is not as active as it should be.
The TSH test, however, does not always detect borderline cases of hypothyroidism. The doctor may order additional tests to measure the levels of thyroid hormone as well as TSH in the patient’s blood. If the doctor thinks that the patient may have Hashimoto’s disease, he or she may test for the presence of abnormal antibodies in the blood. Because Hashimoto’s disease is an autoimmune disorder, there will be two or three types of anti-thyroid antibodies in the patient’s blood in about 90 percent of cases
A woman being tested for hypothyroidism should let her doctor know if she is pregnant or breastfeeding and all patients should be sure their doctors are aware of any recent procedures involving radioactive materials or contrast media.
In some cases, the doctor may also order an ultrasound study of the patient’s neck in order to evaluate the size of the thyroid gland or take a small sample of thyroid tissue in order to make sure that the gland is not cancerous. The usual procedure for obtaining the tissue sample is a fine-needle aspiration biopsy or FNAB. To perform a FNAB, the doctor inserts a thin needle into the thyroid to extract a sample of cells for examination under a microscope. The doctor usually uses an ultrasound monitor to guide the needle. A FNAB can be performed in an outpatient clinic or a doctor’s office; it is safer and less invasive than an open surgical biopsy.
Medications are the treatment of choice for hypothyroidism.
Treatment for hypothyroidism consists of a daily dose of a synthetic form of thyroid hormone sold under the trade names of Synthroid, Levothroid, or Levoxyl. The patient is told that the drug must be taken as directed for the rest of his or her life.
In the early weeks of treatment, the patient will need to see the doctor every four to six weeks to have their TSH level checked and the dose of medication adjusted. After the doctor is satisfied with the dosage level and the patient’s overall health, checkups are done every six to 12 months. The reason for this careful measurement of the medication is that too much of the synthetic hormone increases the risk of osteoporosis in later life or abnormal heart rhythms in the present. Aging, other medications, and changes in weight and general health can also affect how much replacement hormone a patient needs, and regular TSH tests are used to monitor hormone levels. Patients should not switch from one brand of thyroid hormone to another without a doctor’s permission.
Medications and over-the-counter preparations that can affect the body’s absorption of synthetic thyroid hormone include cholestyramine (Questran), antacids that contain aluminum hydroxide, calcium supplements, and iron supplements. A high intake of soy products or a diet high in fiber can also affect the body’s absorption of the hormone, and the patient’s doctor may need to adjust the dosage.
Congenital hypothyroidism or cretinism is also treated with synthetic thyroid hormone. Most hospitals now screen newborns for thyroid problems, because untreated cretinism can lead to lifelong physical and mental developmental disorders.
Regular exercise and a high-fiber diet can help maintain thyroid function and prevent constipation.
Alternative treatments are primarily aimed at strengthening the thyroid and will not eliminate the need for thyroid hormone medications. Herbal remedies to improve thyroid function and relieve symptoms of hypothyroidism include bladder wrack (Fucus vesiculosus), which can be taken in capsule form or as a tea. Some foods, including cabbage, peaches, radishes, soybeans, peanuts, and spinach, can interfere with the production of thyroid hormones. Anyone with hypothyroidism may want to avoid these foods.
The Shoulder Stand yoga position (at least once daily for 20 minutes) is believed to improve thyroid function.
One alternative treatment for hypothyroidism that should not be used is coconut oil. There is no evidence that coconut oil stimulates the thyroid gland, and a few studies suggest that it may actually lower thyroid function.
The Hypothyroidism Revolution is a programme available on the internet as an ebook.
To read a review see: The Hypothyroidism Revolution review
This programme covers natural and dietary treatment of hypothyroidism in great detail.
The prognosis for patients with hypothyroidism is very good, provided they take their medication as directed. They can usually live a normal life with a normal life expectancy. Children with cretinism have a good prognosis if the disorder is caught and treated early; some develop learning disorders, however, in spite of early treatment.
The chief risks to health are related to lack of treatment for hypothyroidism. If low levels of thyroid hormone are not diagnosed and treated, patients are at increased risk of goiter, an enlarged heart, and severe depression. In addition, women with untreated hypothyroidism have a higher risk of giving birth to babies with cleft palate and other birth defects.
One rare but potentially life-threatening complication of long-term untreated hypothyroidism is myxedema coma. In this condition, which is usually triggered by stress or illness, the person becomes extremely sensitive to cold, may be unusually drowsy, or lose consciousness. Heart rate, blood pressure, and breathing may all be abnormally low. Myxedema coma requires emergency treatment in a hospital with intravenous thyroid hormone and intensive care nursing.
There were no proven ways to prevent hypothyroidism as of 2009 because the disorder has so many possible causes.