Hypothyroidism

The Underactive Thyroid

Hypothyroidism refers to a condition in which the amount of thyroid hormones in the body is below normal. This is the most common form of thyroid functional abnormality, and is far more common than an overactive thyroid. Large population studies have shown that as many as one woman in ten over the age of 65 has evidence of the earliest stages of hypothyroidism.

Usually, patients with mild disease feel entirely well. However, some patients with mild hypothyroidism may note improvement in their sense of well-being after being treated with thyroid hormone.

Follow-up studies show that many people with mild thyroid failure eventually develop more severe thyroid failure in later years. Therefore, such patients should be followed closely if treatment is not instituted when the problem is mild and if the patient feels well. Hypothyroidism can occur spontaneously, or it can develop after treatment for hyperthyroidism.

What are the Symptoms?

Mild hypothyroidism may not cause any symptoms. With more severe hypothyroidism you may begin to feel run down, slow, depressed, sluggish, cold, tired, and may lose interest in normal daily activities. Other symptoms may include dryness and brittleness of hair, dry and itchy skin, constipation, muscle cramps, and increased menstrual flow in women.

How is The Diagnosis Made?

Accurate and precise diagnosis of hypothyroidism is now possible. Measurement of the blood level of the thyroid hormone, thyroxine (T4) as well as the pituitary thyroid-stimulating hormone (TSH) may be all that is necessary. A T4 in the low or normal range, plus a high TSH, confirms the diagnosis of thyroid failure. (There is absolutely no evidence that hypothyroidism can be detected by taking your temperature.)

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.