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 Endocrinology 


Hypothyroidism

 


Low Thyroid Hormone.

When the thyroid gland produces below normal amounts of thyroid hormones the condition is known as hypothyroidism –underactive thyroid-. Hypothyroidism is the most common of the conditions affecting the thyroid. It can occur at any age and is more common in women. By age 65, 1 in ten women develop some degree of hypothyroidism.

Also known as Hashimoto's disease, Chronic autoimmune thyroiditis

 

What are the Symptoms?

Hypothyroidism presents in several degrees of intensity of symptoms. In mild cases the patient feels entirely well. With increase severity the patient feels, tired, cold, sluggish, even depress and without interest in their activities. The hair and the skin can turn dry; itching is not unusual as is constipation, muscle cramps, and increase menstrual flow.

How is The Diagnosis Made?

So you or someone you know has most of this symptoms, are you hypothyroid? No so fast, many people can have all of these symptoms and still have a normal thyroid. The diagnosis requires careful laboratory studies. Including the thyroid hormones T4 and T3, a correction factor called T3uptake (or T3u) and a pituitary hormone: Thyroid stimulating Hormone (TSH).

TSH is used as a screening test in most doctors’ offices and even in health fairs. The pituitary regulates your thyroid in much the same way that the thermostat on your living room wall regulates your furnace.

If your pituitary gland senses that there is not enough thyroid hormone in your blood, it will release TSH; TSH stimulates the thyroid, in turn, to increase production and release of thyroid hormone into the blood. When there is enough thyroid hormone in the bloodstream, the pituitary decreases production of TSH. If there is too little thyroid hormone the pituitary will keep increasing the TSH production, when the thyroid can not respond by increasing thyroid hormone, as in hypothyroidism, TSH levels will be elevated.

Secondary Hypothyroidism

In very rare instances, the pituitary gland itself fails, usually due to the presence of a tumor. When this happens, the pituitary no longer stimulates the thyroid properly, and secondary hypothyroidism results. Both T4 and TSH will be low in this condition.

What is the Best Treatment for Hypothyroidism?

Treatment of hypothyroidism is also straight-forward. Thyroid hormone is usually prescribed as pure synthetic thyroxine (T4). Desiccated (dried and powdered) animal thyroid, once the most common form of thyroid therapy, is rarely prescribed today because it also contains triiodothyronine (T3), a rapidly acting thyroid hormone which produces more variable blood levels than pure thyroxine preparations. It also may vary in potency from batch to batch, because it comes from animal thyroid glands, which can vary in their thyroid hormone content. Most endocrinologists switch patients who are taking desiccated thyroid to synthetic thyroxine, which is purer and has a constant level of potency. There is no evidence that desiccated thyroid, a biological preparation, has any advantage over synthetic thyroxine.

Gradually increasing doses of thyroxine are given until the blood levels of T4 and TSH are both in the normal range. In instances where the patient is elderly or has an underlying heart condition, it is extremely important to start with a very low dose of thyroid hormone until the body gets used to the more normal thyroid hormone levels. Since the potency of generic thyroxine has in the past varied considerably, your physician will likely specify a brand name of thyroxine to treat hypothyroidism.

It does not take much thyroxine to treat a hypothyroid patient, and very few patients require more than 150 micrograms daily. On the other hand, thyroid failure is an ongoing process. As a result, a dose that is appropriate for a patient one year may subsequently be too low. Blood tests performed every year or two will guide adjustment of thyroxine. The dose usually needs to be increased during pregnancy. On the other hand, elderly patients require less thyroxine, so that the dose may need to be decreased as a patient ages. Once the proper dosage of medication is achieved, the patient should feel completely well and be free of hypothyroid symptoms.

In those rare instances where the pituitary gland is the problem, the pituitary itself will require treatment and other types of medications may also be necessary. This is because the pituitary controls not only thyroid function, but the function of many other glands within the body, including the reproductive glands and the adrenal glands.

Problems with Too Much or Too Little Hormone

If you are being treated for an underactive thyroid and are not taking enough thyroid hormone, some of the symptoms of hypothyroidism such as sluggishness, mental dullness, feeling cold, or muscle cramps may persist. In addition, you may have problems with elevation of cholesterol which could increase your risk for hardening of the arteries (arteriosclerosis).

If you take too much thyroid hormone, you may have symptoms mimicking an overactive thyroid, including nervousness, palpitations, insomnia, and tremor. In addition, thyroid hormone excess may also cause excessive calcium loss from your bones, increasing your risk for fractures in later years.

Long Term Follow-up

Above all, do not forget to return to your doctor for follow-up once a year so that your thyroid hormone and TSH levels can be rechecked. Similarly, if you change doctors, remind your new physician that you have an ongoing thyroid problem that must be reevaluated at the time of your annual physical examination.

Other Family Members at Risk

Since the most common type of thyroid gland failure is an inherited condition called Hashimoto's acute thyroiditis, examinations of the members of your family may reveal other individuals with thyroid problems.