Screening Tests for Thyroid Dysfunction

The thyroid is a gland situated in the front of the neck that secretes two hormones, thyroxine or T4 and thyronine or T3. The thyroid hormones influence important metabolic processes in the body. Increase in thyroid hormone production by the thyroid gland results in a condition called hyperthyroidism, whereas a decrease in thyroid hormones production results in hypothyroidism. Untreated hyperthyroidism can lead to atrial fibrillation or abnormal heart rhythm, heart failure, osteoporosis or bone thinning, and neuropsychiatric problems. Hypothyroidism, if untreated, can lead to fatigue, weight gain, mental slowing, heart failure, and increase in cholesterol levels.

Secretion of thyroid hormones is controlled by a hormone secreted by the pituitary gland (a small gland at the base of the skull) called thyroid stimulating hormone or TSH. If thyroid hormone levels fall (as in hypothyroidism), it is followed by an increased secretion of TSH, which tries to maintain the level of thyroid hormone. On the other hand, if the level of thyroid hormone increases (as in hyperthyroidism), the level of TSH falls. Measurement of the thyroid hormone levels T3 and T4 as well as TSH help to estimate thyroid function.

Subclinical thyroid dysfunction occurs in about 3 to 8 percent individuals of the general population. It is found more commonly in women and older individuals. People with subclinical thyroid dysfunction do not suffer from any symptoms. Their T3 and T4 levels are normal; however, their TSH may be either high or low. These patients could progress to thyroid dysfunction. Subclinical hyperthyroidism (with low TSH levels) may be associated with atrial fibrillation, dementia or forgetfulness, and osteoporosis. Subclinical hypothyroidism may be associated with poor obstetric outcomes and can affect development of brain function in children. Screening for thyroid function could help to detect thyroid dysfunction in these individuals, and enable early treatment.

Effective treatments for thyroid dysfunction are available, thus early diagnosis and timely treatment is definitely useful in preventing complications.