TSH levels are altered by the timing of levothyroxine administration
TSH levels are altered by the timing of levothyroxine administration
SUMMARY
BACKGROUND http://www.thyroid.org/wp-content/uploads/publications/clinthy/volume21/issue9/clinthy_v219_3_5.pdf” Levothyroxine (L-T4) has a narrow therapeutic index, which is influenced by intestinal absorption. Administration with food, other medications, and even certain beverages such as coffee may result in interference with L-T4 absorption. The aim of this study was to determine whether taking L-T4 with breakfast or at bedtime results in significant elevations in serum thyrotropin (TSH) as compared with its traditional administration after an overnight fast, 1 hour before breakfast.
METHODS The study subjects were patients 18 to 75 years of age who had hypothyroidism for at least 2 years or had thyroid cancer with no evidence of persistent disease. The patients with hypothyroidism were required to have a stable TSH for 6 months while taking one of the two most popular brands of L-T4. Those with thyroid cancer were required to have a TSH level ranging from 0.01 to 0.5 ?IU/ml. Patients were excluded from the study if they were pregnant, were taking medications known to interfere with L-T4 absorption or metabolism, or had a chronic illness such as heart disease, diabetes, or pulmonary, gastrointestinal, or renal disease.
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