1. What is Hypothyroidism?
Hypothyroidism is underactivity of the thyroid gland that leads to inadequate production of thyroid hormones and a slowing of vital body functions. The thyroid gland secretes thyroid hormones, which control the speed at which the body’s chemical functions proceed (metabolic rate). Thyroid hormones affect many vital body functions, such as the heart rate, the rate at which calories are burned, skin maintenance, growth, heat production, fertility, and digestion. There are two thyroid hormones:
- T4: Thyroxine (also called tetraiodothyronine)
- T3: Triiodothyronine
The pituitary gland produces thyroid-stimulating hormone (TSH), which stimulates the thyroid gland to produce thyroid hormones. The pituitary gland slows or speeds the release of TSH, depending on whether the levels of thyroid hormones circulating in the blood are getting too high or too low.
Primary hypothyroidism results from a disorder of the thyroid gland itself. The most common cause is
- Hashimoto thyroiditis: Hypothyroidism develops as the thyroid is gradually destroyed.
Other causes of primary hypothyroidism include
- Thyroid inflammation (thyroiditis)
- Treatment of hyperthyroidismor thyroid cancer
- Lack of iodine
- Radiation to the head and neck
- Inherited disorders that prevent the thyroid gland from making or secreting enough hormones
Secondary hypothyroidism occurs when the pituitary gland fails to secrete enough thyroid-stimulating hormone (TSH), which is necessary for normal stimulation of the thyroid. Secondary hypothyroidism is much rarer than primary.
2. Common Signs and Symptoms of Hypothyroidism
Insufficient thyroid hormones cause body functions to slow. Symptoms are subtle and develop gradually. Some of them may be mistaken for depression, especially among older people.
- Facial expressions become dull.
- The voice is hoarse and speech is slow.
- Eyelids droop.
- The eyes and face become puffy.
- The hair becomes sparse, coarse, and dry.
- The skin becomes coarse, dry, scaly, and thick.
Many people with hypothyroidism are fatigued, gain weight, become constipated, develop muscle cramps, and are unable to tolerate cold. Some people develop carpal tunnel syndrome, which makes the hands tingle or hurt. The pulse may slow, the palms and soles may appear slightly orange (carotenemia), and the side parts of the eyebrows slowly fall out. Some people, especially older people, may appear confused, forgetful, or demented—signs that can easily be mistaken for Alzheimer disease or other forms of dementia. Women with hypothyroidism may have changes in their menstrual periods. People with hypothyroidism frequently have high levels of cholesterol in their blood.
3. How is Hypothyroidism diagnosed?
Hypothyroidism may be suspected based on the symptoms and findings on physical examination.Usually hypothyroidism can be diagnosed with one simple blood test: the measurement of TSH. If the thyroid gland is underactive, the level of TSH is high.
In those rare cases of hypothyroidism caused by inadequate secretion of TSH, a second blood test is needed. This blood test measures the level of the thyroid hormone T4 (thyroxine, or tetraiodothyronine). A low level confirms the diagnosis of hypothyroidism.
4. How is it treated?
Treatment involves replacing thyroid hormone using one of several oral preparations. The preferred form of hormone replacement is synthetic T4 (levothyroxine).Treatment begins with small doses of thyroid hormone, because too large a dose can cause serious side effects, although large doses may eventually be necessary. The starting dose and the rate of increase are especially small in older people, who are often most at risk of side effects. The dose is gradually increased until the levels of TSH in the person’s blood return to normal. During pregnancy, doses usually need to be increased.
Disclaimer: The content in the post is intended to be for informational purposes only and not to replace professional medical advice, diagnosis, or treatment. Always seek the advice of your medical provider or other qualified health care provider with any questions you may have regarding a medical condition.
