Hypothyroidism
Hypothyroidism is the most common thyroid disorder. It occurs when the thyroid gland becomes underactive and does not produce enough thyroid hormone, producing a reduction of the metabolic rate and a decline in normal bodily functions. It is estimated that up to 10% of women over the age of 65 show some signs of hypothyroidism. Although less common, hypothyroidism does occur among younger adults. It can also occur in newborns, a term referred to as cretinism, which has been associated with mental disability, jaundice, poor feeding, breathing difficulties and growth abnormalities. Childhood hypothyroidism is characterized by delayed growth and concerns with mental development but with prompt treatment, problems can be minimized.
The most common cause of adult hypothyroidism is Hashimoto's thyroiditis, caused by an autoimmune reaction involving the production of antibodies that attack and gradually destroy the thyroid gland. Women are eight times more likely than men to develop Hashimoto's thyroiditis, especially with increasing age. It also has a genetic link or can be associated with syndromes of genetic abnormalities, such as Turner's syndrome, Klinefelter's syndrome and Down syndrome.
Hypothyroidism can also be caused by treatments for hyperthyroidism, meaning treatment (medications or radioactive iodine treatments) for hyperthyroidism may make the thyroid gland inactive, or in cases where the thyroid is surgically removed. Either may result in a lack of thyroid hormones, causing hypothyroidism.
The thyroid gland requires iodine to function properly. A chronic lack of iodine means that less thyroid hormone can be produced and this causes the thyroid to enlarge. Since salt manufacturers now add iodine to salt, this form of hypothyroidism is extremely rare in North America but it is still the major cause of hypothyroidism in underdeveloped countries, where iodine is often lacking in the diet.
Some rare inherited disorders cause enzyme abnormalities in the thyroid gland that disable the gland’s ability to produce hormones. Secondary hypothyroidism may occur if the pituitary gland, located in the brain, is malfunctioning and not producing a thyroid-stimulating hormone (TSH) needed to stimulate the thyroid gland. Fortunately, these disorders are quite rare and not a major cause of hypothyroidism. Hormones T4 and T3 are lacking and results in a reduction to the body's metabolic rate. Symptoms may not be obvious and hypothyroidism may sometimes be mistaken for other conditions.
People with hypothyroidism often experience the following symptoms
- fatigue or feeling sluggish
- weakness
- cold intolerance
- weight gain
- constipation
- depression
- irritability
- dry, scaly skin
- coarse and dry hair
- hair loss
- muscle cramps
- increased menstrual flow
- slower heart rate
- confusion or forgetfulness (often mistaken for dementia in seniors)
If hypothyroidism isn't treated, symptoms will progress and may lead to a more serious condition known as myxedema. With myxedema, the body’s temperature drops, anemia occurs and there is a risk of congestive heart failure. Myxedema coma occurs in some people with severe hypothyroidisms who are exposed to some kind of stress like infection, severe cold, trauma or the use of sedatives. Symptoms include loss of consciousness, seizures, slowed breathing, and lack of blood flowing to the brain.
Treating hypothyroidism requires replacing hormones with synthetic or natural thyroid hormones. The easiest and most effective thyroid hormone replacement involves a synthetic form of T4 that is taken orally. These tablets are available in a variety of doses adjusted for each individual until the correct hormone levels in the blood are attained and symptoms are managed. Natural thyroid supplements, which usually contain thyroid glands from animals, are rarely used because they can cause allergic reactions and do not provide a consistent dose of T4. People with mild hypothyroidism might feel fine and not require treatment, while others will be bothered by symptoms and require treatment. Hypothyroidism usually worsens over time and even mild cases should be regularly monitored.
If a dysfunctional pituitary gland is the cause of hypothyroidism, it will need to be treated. The pituitary gland controls many other glands in the body as well and several medications may be needed. Consult your healthcare provider for more information.
If your healthcare provider suspects hypothyroidism, blood tests can assess the function of the thyroid gland. Levels of T4 in the blood are measured, along with thyroid-stimulating hormone (TSH) produced by the pituitary gland. High levels of TSH suggest that the thyroid is underactive and that the pituitary is overcompensating by making excessive hormones to stimulate the thyroid gland. In cases where secondary hypothyroidism is present, the pituitary gland is malfunctioning and both T4 and TSH levels in the blood are low. Thyroid scans, using radioactive iodine or technetium, allow healthcare providers to observe the thyroid gland and identify areas that are less active.
Source:
Calgary Regional Health Authority |
