Hypothyroidism is a common disease that is successfully treated with the replacement of thyroid hormones in the form of levothyroxine. Levothyroxine is drug used in the first line of substitution therapy because it appropriately mimics physiological secretion of thyroxine (T4) and its peripheral conversion to triiodothyronine (T3). However, due to its narrow therapeutic index, and because it is administered at very low doses (micrograms - μg), it is particularly sensitive to the absorption phase interactions, which are due to its narrow therapeutic index, mainly clinically significant. In pregnancy, one of the goals is to maintain the values of thyroid stimulating hormone (TSH) in the lower part of the reference interval (below 2,5 milli-International units - mIU/L) for a proper child development. Also, due to increased nutritional needs during pregnancy, nutritional supplements are commonly used by pregnant women on their own initiative, but also often recommended by healthcare personnel. Reviewing the literature, we did not find high quality evidence to suggest the existence or to refute the interaction between dietary supplements for pregnant women and the absorption of levothyroxine. The aim of this study is to investigate this potential interaction between dietary supplements used in pregnancy and levothyroxine absorption in order to test the safety of the use of these preparations in pregnant women who are on replacement therapy with levothyroxine.
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Change in thyrothropin
Timeframe: 8 weeks