How is hypothyroidism diagnosed?
Many symptoms of hypothyroidism can occur in other diseases, so hypothyroidism usually
cannot be diagnosed based on symptoms alone. Health care providers take a medical
history and perform a thorough physical examination. Providers may then use several
tests to confirm a diagnosis of hypothyroidism and find its cause.
Thyroid-stimulating Hormone (TSH) Test
The ultrasensitive TSH test is usually the first test a doctor performs. This test
is the most accurate measure of thyroid activity available.
The TSH test is based on the way TSH and thyroid hormone work together. The pituitary
gland boosts TSH production when the thyroid is not making enough thyroid hormone;
the thyroid normally responds to TSH by making more hormone. Then, when the body
has enough thyroid hormone circulating in the blood, TSH output drops. In people
who produce too little thyroid hormone, the pituitary makes TSH continuously, trying
to get the thyroid to produce more thyroid hormone.
Generally, a TSH reading above normal means a person has hypothyroidism and a reading
below normal means a person has hyperthyroidism.
Health care providers may conduct additional tests to help confirm the diagnosis
or determine the cause of hypothyroidism.
The T4 test measures the actual amount of circulating thyroid hormone
in the blood. In hypothyroidism, the level of T4 in the blood is lower
The thyroid autoantibody test looks for the presence of
thyroid autoantibodies. Most people with Hashimoto’s disease have these antibodies,
but people whose hypothyroidism is caused by other conditions do not.
How is Hypothyroidism treated?
Hypothyroidism is treated with synthetic thyroxine, which is identical to the T4
made by the thyroid. The exact dose will depend on the patient’s age and weight,
the severity of the hypothyroidism, the presence of other health problems, and whether
the person is taking other drugs that might interfere with how well the body uses
Health care providers test TSH levels about 6 to 8 weeks after a patient begins
taking thyroid hormone and make any necessary adjustments to the dose. Each time
the dose is adjusted, the blood is tested again. Once a stable dose is reached,
blood tests are normally repeated in 6 months and then once a year after that.
Hypothyroidism can almost always be completely controlled with synthetic thyroxine,
as long as the recommended dose is taken every day as instructed.
Endocrine and Metabolic Diseases Information Service