By hypothyroidism, the thyroid gland is producing too less hormones to stimulate the metabolism, or the body is not able to utilize the hormones. The lack of thyroid hormones slows down the metabolism and thus all the activities in the body, giving a combination of many symptoms related to slowness of bodily processes.

Hypothyroidism is common, but the frequency of the condition is not well determined. Some authorities estimate that 0.5% of the total American population have the disease to some degree. The frequency is much greater among people over 50 years of age than among young people.

THE SYMPTOMS AND COMPLICATIONS OF HYPOTHYROIDISM

The most common early symptoms are: Mental and physical fatigue, weakness, weight gain or over-weight, and depression.

One or more of these symptoms also use to appear early: Constipation, sensitivity to coldness, cold hands and feet, thick tongue, decreased sweating, dry hair, thin brittle hair, thin brittle nails, muscle and joint pain, pale or yellowish skin, rashes and itching.

One or more of these symptoms usually appear later: Poor memory, slow thought process, drowsiness, slow speech, thinning of eyebrows, hoarseness, low blood pressure, poor circulation, dry and flaky skin, decreased taste and smell, menstrual irregularities, skin thickening, puffy face, puffy hands and feet, swelling of extremities, overall swelling, muscle spasms, muscle atrophy, joint stiffness.

In children or young persons hypothyroidism may give developmental problems, like disturbed tooth development and short stature.

Hypothyroidism increases the risk of elevated cholesterol levels, heart disease and diabetes (diabetes mellitus). This occurs even by moderately decreased thyroid production.

THE THYROID GLAND AND ITS HORMONES

To understand the hypothyroidism, some knowledge about the thyroid gland and its hormones is essential.

The thyroid gland produces hormones that accelerate and in other wise regulate metabolism. A part of metabolism is the process of breaking down energy containing nutrients, and using the energy to produce molecules that all the processes and activities in the body use as fuel. Another part is the production of molecules that the body use as building materials.

The thyroid makes four hormones: Thyroxin (T4), triiodothyronine (T3), diiodothyronine (T2) and monoiodothyronine (T1). The hormones contain iodine, and the figures tell about the number of iodine atoms in each hormone molecule. T3 is not made directly, but is produced from T4. T3 is a more efficient hormone than T4. Therefore this conversion is important.

The pituitary, a gland under the brain, produces a hormone called thyrotropin or thyroid stimulating hormone (TSH) that enhances the activity of the thyroid gland. If the body has too less thyroid hormone in the blood, the pituitary produces more thyrotropin. This makes the thyroid gland speed up its own production. By a too heavy thyroid hormone concentration, less thyrotropin is produced by the pituitary, and the thyroid gland slows down. This feed-back mechanism regulates the metabolism of the whole body.