While overt hypothyroidism affects one to two percent of the population, incidence of subclinical hypothyroidism are more common. It has been estimated that ten percent of the general population and 20 percent of older women suffer from subclinical hypothyroidism. Often this condition goes undetected as the symptoms are often vague and nonspecific. Tests for the presence of autoantibodies may also be used to distinguish autoimmune disorders like Hashimoto's thyroiditis. Hypothyroidism treatment involves thyroid hormone replacement therapy with levothyroxine for the life of the patient.
Synthetic thyroxine comes in pill form and produces very few side effects.
During development of hypothyroidism, serum TSH is the optimal test for diagnosing and assessing all phases of disease. A FT 4 E test can help quantitate the severity of the disease. Following initiation of T4 replacement therapy or a change in T4 dosage, normalization of serum T4 can be achieved within weeks. A FT4E test will most accurately reflect the efficacy of the T4 replacement therapy during the acute phase of treatment. Serum TSH is misleadingly high in this phase because of the lag in the pituitary reset of TSH secretion.