Abstract
Levothyroxine belongs to the most frequently used medication. It is used to substitute lacking hormone, physiologically produced by thyroid gland.
Metabolically effective is triiodothyronine, which arises due to activity of deiodinases directed to prohormone thyroxin. Considering thyroxin biological half-life 7 days the treatment effect starts gradually.
Thyroxin is absorbed by mucosa of stomach, duodenum and part of small intestine. Its resorption and thus reduced effect of the medication may be influenced by many circumstances, for instance illness of gastrointestinal tract, other used medication, certain agents in the environmental circumstances including hormonal disruptors.
Thyroid cancer is one of the most prevalent solid tumor types throughout the world with a rising incidence, particularly in women. There is a consistent evidence that suppression of thyreostimulation hormone is a basic approach to treat thyroid carcinoma.
In such indication, we administer supraphysiological dosage of thyroid hormones. New diagnostic approaches mainly methods of molecular genetics and new imaging methods may help in definition of risks and benefits of suppressive treatment and selection of patients, in which we may use less aggressive treatment.