Hypothyroidism - Introduction

Hypothyroidism

Hypothyroidism occurs when thyroxine (T4) levels drop to the point that the body begins to slow down. Hypothyroidism was first diagnosed in the late nineteenth century when doctors observed thatsurgical removalof the thyroid resulted in theswelling of the hands, face, feet, and tissues around the eyes. They named this syndrome myxedema and correctly concluded that it was the outcome of the absence of substances, thyroid hormones, normally produced by the thyroid gland. Hypothyroidism is usually progressive and irreversible. Treatment, however, is nearly always completely successful and allows a patient to live a fully normal life.

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Subclinical Hypothyroidism

Subclinical hypothyroidism, also called early-stage hypothyroidism, is a condition in which thyrotropin (TSH) levels have started to increase in response to an early decline in T4 levels in the thyroid. However, blood tests for T4 are still normal. The patient may have mild symptoms (usually slight fatigue) or even none at all. Subclinical hypothyroidism is very common (affecting about 10 million Americans) and is a topic of considerable debate among professionals because it is not clear how to manage this condition.

For instance, subclinical hypothyroidism does not progress to the full-blown disorder in most people. Experts estimate that each year approximately 2 - 5% of people with subclinical hypothyroidism will go on to develop overt hypothyroidism. Other factors associated with a higher risk includebeing an older woman (up to 20% of women over age 60 have subclinical hypothyroidism), having a goiter (enlarged thyroid gland) or thyroid antibodies, or harboring immune factors that suggest an autoimmune condition.

Subclinical hypothyroidism is determined on the basis of the TSH laboratory blood tests. According to a 2004 consensus statement from the American Thyroid Association, the American Association of Clinical Endocrinologists, and the Endocrine Society the normal range of TSH concentration falls between 0.45 and 4.5 mU/L. Patients in the subclinical hypothyroidism have TSH levels between 4.5 MU/L and 10mU/L. Patients with levels greater than 10mU/L are considered to have overt hypothyroidism and should be treated with medication.

For patients in the subclinical hypothyroidism range, treatment decisions are less clear. The consensus committee recommended against routine treatment for patients with subclinical hypothyroidism, but did suggest repeat screenings of thyroid function every 6 to 12 months to detect any changes in TSH levels. However, these are general guidelines and individual cases and risk factors may differ. Patients should discuss with their doctor the course of action that is most appropriate for them.