Sunday, June 24, 2007
Wednesday, June 20, 2007
The differential diagnosis of hypothyroidism includes nonthyroidal illness (i.e., decreased T3 or T4 , or both, without clinical hypothyroidism), euthyroid hypothyroxinemia (decreased T4 caused by decreased thyroid-binding globulin), and drugs that inhibit T4 binding (salicylates, phenytoin, and phenobarbital). Once hypothyroidism has been diagnosed, the most important clinical distinction is between primary and secondary hypothyroidism. The clinical and laboratory similarities between myxedema coma and other life-threatening causes of the comatose state may make its diagnosis extremely difficult. Regarding hypothyroid myopathy, the muscular appearance, stiffness, and exacerbation by cold may suggest a mild form of myotonia congenita, which can present in adulthood. Although the stiffness noted in patients with pyramidal and extrapyramidal diseases may appear similar to that of hypothyroid myopathy, the characteristic history, appearance, and laboratory studies usually permit the diagnosis of hypothyroidism.
The combination of a low T4 level and an elevated thyroid-stimulating hormone (TSH) level is virtually diagnostic of primary hypothyroidism, because TSH elevation does not occur in central hypothyroidism. Further delineation between primary and secondary hypothyroidism is dependent on history, examination, and other laboratory studies. In addition to TFTs, other laboratory abnormalities have been described, including anemia (normocytic-normochromic, microcytic-hypochromic, or macrocytic) and hyponatremia (factitious due to hyperlipidemia or secondary to impaired free water excretion), as well as elevated serum creatine kinase, myoglobin, and prolactin. Because of the possibility of concomitant adrenal insufficiency, a serum cortisol level should also be obtained. The EEG may show slowing of the posterior dominant rhythm and a generalized voltage decrease, as well as triphasic waves that disappear with replacement therapy. CSF analysis may reveal an elevated protein content which may exceed 100 mg/dl.
The treatment of hypothyroidism, regardless of cause, consists of thyroid hormone replacement. Even in the setting of hypothyroid-induced seizures, achievement of the euthyroid state facilitates control. Precipitants of myxedema coma (e.g., infection, cold exposure, certain drugs phenothiazines, narcotics, and sedative-hypnotics, phenytoin, rifampin , and other stressors surgery, trauma ) require correction.
Prognosis and Future Perspectives.
With early recognition and treatment, as well as improved intensive supportive care, the mortality rate of myxedema coma has decreased from roughly 50 to 70 percent to around 15 to 20 percent.
Without early recognition and prompt institution of replacement therapy, the prognosis is grave.
Monday, June 18, 2007
Thursday, June 14, 2007
Your thyroid gland produces two main hormones, thyroxine (T-4) and triiodothyronine (T-3), that influence every cell in your body. They maintain the rate at which your body uses fats and carbohydrates, help control your body temperature, influence your heart rate and help regulate the production of protein. Your thyroid gland also produces calcitonin, a hormone that regulates the amount of calcium in your blood.
The rate at which thyroxine and triiodothyronine are released is controlled by your pituitary gland and your hypothalamus — an area at the base of your brain that acts as a thermostat for your whole system. The hypothalamus signals your pituitary gland to make a hormone called thyroid-stimulating hormone (TSH). Your pituitary gland then releases TSH — the amount depends on how much thyroxine and triiodothyronine are in your blood. Finally, your thyroid gland regulates its production of hormones based on the amount of TSH it receives.
Although this process usually works well, the thyroid sometimes fails to produce enough hormones. This may be due to a number of different factors, including:
- Autoimmune disease (Hashimoto's thyroiditis). Autoimmune disorders occur when your immune system produces antibodies that attack your own tissues. Sometimes this process occurs within the thyroid gland. Scientists aren't sure why the body produces antibodies against itself. Some think a virus or bacteria might trigger the response, while others believe a genetic flaw may be involved. Most likely, autoimmune diseases result from more than one factor. But however it happens, these antibodies affect the thyroid's ability to produce hormones.
- Treatment for hyperthyroidism. People who produce too much thyroid hormone (hyperthyroidism) are often treated with radioactive iodine or anti-thyroid medications to reduce their thyroid function. However, function can be reduced too much, resulting in hypothyroidism.
- Radiation therapy. Radiation used to treat cancers of the head and neck can affect your thyroid gland and may lead to hypothyroidism.
- Thyroid surgery. Removing all or a large portion of your thyroid can diminish or halt hormone production. In that case, you'll need to take thyroid hormones for life.
- Medications. A number of medications can contribute to hypothyroidism. One such medication is lithium, which is used to treat certain psychiatric disorders. If you're taking medication, ask your doctor about its effect on your thyroid gland.
- Congenital disease. Approximately one in 3,000 babies in the United States is born with a defective thyroid gland or no thyroid gland at all. In most cases, the thyroid gland didn't develop normally for unknown reasons, but some children have an inherited form of the disorder. Often, infants with congenital hypothyroidism appear normal at birth. That's one reason why most states now require newborn thyroid screening.
- Pituitary disorder. A relatively rare cause of hypothyroidism is the failure of the pituitary gland to produce enough TSH — usually due to a benign tumor of the pituitary gland.
- Pregnancy. Some women develop hypothyroidism during or after pregnancy (postpartum hypothyroidism), often because they produce antibodies to their own thyroid gland. Left untreated, hypothyroidism increases the risk of miscarriage, premature delivery and preeclampsia — a condition that causes a significant rise in a woman's blood pressure during the last three months of pregnancy. It can also seriously affect the developing fetus.
- Iodine deficiency. The trace mineral iodine — found primarily in seafood, seaweed, plants grown in iodine-rich soil and iodized salt — is essential for the production of thyroid hormones. In some parts of the world, iodine deficiency is common, but the addition of iodine to table salt has virtually eliminated this problem in the United States.
Although anyone can develop hypothyroidism, it occurs mainly in women older than 50, and the risk of developing the disorder increases with age.
- Have a close relative, such as a parent or grandparent, with an autoimmune disease
- Have been treated with radioactive iodine or anti-thyroid medications
- Received radiation to your neck or upper chest
- Have had thyroid surgery (partial thyroidectomy)
Wednesday, June 13, 2007
- Goiter. Constant stimulation of your thyroid to release more hormones may cause the gland to become larger — a condition known as goiter. Hashimoto's thyroiditis is one of the most common causes of a goiter. Although generally not uncomfortable, a large goiter can affect your appearance and may interfere with swallowing or breathing.
- Heart problems. Hypothyroidism may also be associated with an increased risk of heart disease, primarily because high levels of low-density lipoprotein (LDL) cholesterol — the "bad" cholesterol — can occur in people with an underactive thyroid. Even subclinical hypothyroidism, a more benign condition than true hypothyroidism, can cause an increase in total cholesterol levels and impair the pumping ability of your heart. Hypothyroidism can also lead to an enlarged heart and heart failure.
- Mental health issues. Depression may occur early in hypothyroidism and may become more severe over time. Hypothyroidism can also cause slowed mental functioning.
- Myxedema. This rare, life-threatening condition is the result of long-term, undiagnosed hypothyroidism. Its symptoms include intense cold intolerance and drowsiness followed by profound lethargy and unconsciousness. A myxedema coma may be triggered by sedatives, infection or other stress on your body. If you have symptoms of myxedema, you need immediate emergency medical treatment.
- Birth defects. Babies born to women with untreated thyroid disease may have a higher risk of birth defects than do babies born to healthy mothers. These children are more prone to serious intellectual and developmental problems.
Infants with untreated hypothyroidism present at birth are also at risk of serious problems with both physical and mental development. But if the condition is diagnosed within the first few months of life, the chances of normal development are excellent.
Tuesday, June 12, 2007
Although hypothyroidism most often affects middle-aged and older women, anyone can develop the condition, including infants and teenagers. Initially, babies born without a thyroid gland or with a gland that doesn't work properly may have few signs and symptoms. When newborns do have problems with hypothyroidism, they may include:
- Yellowing of the skin and whites of the eyes (jaundice). In most cases, this occurs when a baby's liver can't metabolize a molecule called bilirubin, which normally forms when the body recycles old or damaged red blood cells.
- Frequent choking.
- A large, protruding tongue.
- Poor muscle tone
- Excessive sleepiness
In general, children and teens who develop hypothyroidism have the same signs and symptoms as adults do, but they may also experience:
- Poor growth, resulting in short stature
- Delayed development of permanent teeth
- Delayed puberty
- Poor mental development
Monday, June 11, 2007
- The most common thyroid disorder occurring around or during pregnancy is thyroid hormone deficiency, or hypothyroidism.
Hypothyroidism can cause a variety of changes in a woman's menstrual periods: irregularity, heavy periods, or loss of periods. When hypothyroidism is severe, it can reduce a woman's chances of becoming pregnant. Checking thyroid gland function with a simple blood test is an important part of evaluating a woman who has trouble becoming pregnant. If detected, an underactive thyroid gland can be easily treated with thyroid hormone replacement therapy. If thyroid blood tests are normal, however, treating an infertile woman with thyroid hormones will not help at all, and may cause other problems.
- Because some of the symptoms of hypothyroidism such as tiredness and weight gain are already quite common in pregnant women, it is often overlooked and not considered as a possible cause of these symptoms. Blood tests, particularly measuring the TSN level, can determine whether a pregnant woman's problems are due to hypothyroidism or not.
Since thyroid medications (particularly Levothyroxine) are essentially identical to the thyroid hormone made by the normal thyroid gland, a woman with an underactive thyroid gland can feel confident that it is perfectly safe to take thyroid hormone medication during pregnancy. There are no side effects for the mother or the baby as long as the proper dose is used. In the case where hypothyroidism in the mother is NOT detected, the thyroid will still develop normally in the baby.
- Women with previously treated hypothyroidism should be aware that their dose of medication may have to be increased during pregnancy. They should contact their doctor, who should check their blood level of TSH periodically throughout pregnancy to see if their medication dose needs adjustment. Thyroid function tests should continue to be reviewed every 2-3 months throughout the pregnancy. After delivery, the thyroxine dose should be returned to the pre-pregnancy dose and thyroid function tests reviewed two months later.
Wednesday, June 06, 2007
Hypothyroidism is usually quite easy to treat (for most people)! The easiest and most effective treatment is simply taking a thyroid hormone pill (Levothyroxine) once a day, preferably in the morning. This medication is a pure synthetic form of T4 which is made in a laboratory to be an exact replacement for the T4 that the human thyroid gland normally secretes. It comes in multiple strengths, which means that an appropriate dosage can almost always be found for each patient. The dosage should be re-evaluated and possibly adjusted monthly until the proper level is established. The dose should then be re-evaluated at least annually. If you are on this medication, make sure your physician knows it so he/she can check the levels at least yearly.
Tuesday, June 05, 2007
The next question is: When is low too low, and when is high too high? Blood levels have "normal" ranges, but other factors need to be taken into account as well, such as the presence or absence of symptoms. You should discuss your levels with your doctor so you can interpret how they are helping (or not?) fix your problems.
Oh, if only it were this simple all the time!
Monday, June 04, 2007
- Hypothyroidism is a condition in which the body lacks sufficient thyroid hormone.
Since the main purpose of thyroid hormone is to "run the body's metabolism", it is understandable that people with this condition will have symptoms associated with a slow metabolism. Over five million Americans have this common medical condition. In fact, as many as ten percent of women may have some degree of thyroid hormone deficiency. Hypothyroidism is more common than you would believe...and, millions of people are currently hypothyroid and don't know it!
- There are two fairly common causes of hypothyroidism.
The first is a result of previous (or currently ongoing) inflammation of the thyroid gland which leaves a large percentage of the cells of the thyroid damaged (or dead) and incapable of producing sufficient hormone. The most common cause of thyroid gland failure is called autoimmune thyroiditis (also called Hashimoto's thyroiditis), a form of thyroid inflammation caused by the patient's own immune system. The second major cause is the broad category of "medical treatments". As noted on a number of our other pages, the treatment of many thyroid conditions warrants surgical removal of a portion or all of the thyroid gland. If the total mass of thyroid producing cells left within the body are not enough to meet the needs of the body, the patient will develop hypothyroidism. Remember, this is often the goal of the surgery as seen in surgery for thyroid cancer. But at other times, the surgery will be to remove a worrisome nodule, leaving half of the thyroid in the neck undisturbed. Sometimes (often), this remaining thyroid lobe and isthmus will produce enough hormone to meet the demands of the body. For other patients, however, it may become apparent years later that the remaining thyroid just can't quite keep up with demand. Similarly, goiters and some other thyroid conditions can be treated with radioactive iodine therapy. The aim of the radioactive iodine therapy (for benign conditions) is to kill a portion of the thyroid to prevent goiters from growing larger, or producing too much hormone (hyperthyroidism). Occasionally, (often?) the result of radioactive iodine treatment will be that too many cells are damaged so the patient often becomes hypothyroid a year or two later. This is O.K. and usually greatly preferred over the original problem. There are several other rare causes of hypothyroidism, one of them being a completely "normal" thyroid gland which is not making enough hormone because of a problem in the pituitary gland. If the pituitary does not produce enough Thyroid Stimulating Hormone (TSH) then the thyroid simply does not have the "signal" to make hormone, so it doesn't.
Symptoms of Hypothyroidism
- Weight gain or increased difficulty losing weight
- Coarse, dry hair Dry, rough pale skin
- Hair loss
- Cold intolerance (can't tolerate the cold like those around you)
- Muscle cramps and frequent muscle aches
- Memory loss
- Abnormal menstrual cycles
- Decreased libido
Each individual patient will have any number of these symptoms which will vary with the severity of the thyroid hormone deficiency and the length of time the body has been deprived of the proper amount of hormone. Some patients will have one of these symptoms as their main complaint, while another will not have that problem at all and will be suffering from a different symptom. Most will have a combination of a number of these symptoms. Occasionally, some patients with hypothyroidism have no symptoms at all, or they are just so subtle that they go unnoticed.
Note: Although this may sound obvious, if you have these symptoms, you need to discuss them with your doctor and probably seek the skills of an endocrinologist. If you have already been diagnosed and treated for hypothyroidism and you continue to have any or all of these symptoms, you need to discuss it with your physician. Although treatment of hypothyroidism can be quite easy in some individuals, others will have a difficult time finding the right type and amount of replacement thyroid hormone.