Hypothyroidism, or what is known as underactive thyroid, is a very common endocrine condition experienced by an estimated 2% of the general population, although increased in women and with advanced age. Thyroid hormone is critical for adequate neurological development, heart rate, thermoregulation, menstruation, overall metabolism, and many other processes.
Symptoms of hypothyroidism include fatigue, lethargy, cold intolerance, slow heart rate, irregular menstrual periods, muscle weakness, weight gain, infertility, drop in body temperature, and depression.
The diagnosis of primary hypothyroidism should be made only when the pituitary hormone TSH exceeds the upper limits of normal for that assay (for most labs is above 5 mU/L). It is called subclinical hypothyroidism when the TSH is elevated but the thyroid hormone level remains normal.
There are many causes of an underactive thyroid. In the United States, hypothyroidism is usually due to an autoimmune process known as Hashimotos disease, where antibodies directly attack the thyroid gland. Hashimotos is easily diagnosed by measuring such indicators in the blood, even though these antibodies may take weeks, months, or years to render someone as hypothyroid. Antibody presence, however, does not mean that hypothyroidism is inevitable.
The presence of symptoms usually varies depending on the person. The number of symptoms may not correlate with the severity of the condition.
Hypothyroidism is treated with thyroid hormone replacement therapy and blood levels of TSH are used to find the correct replacement dosage.
As always, discuss your symptoms with your doctor before starting or changing thyroid hormone therapy.