Coffee is a mixture of many substances and nutriceuticals, and its chemical composition is determined by many factors (ie, roasting, grinding, extraction). Previous reports of coffee interaction with L-T4 have only involved Italian coffee (ie, espresso), this is the first known case of an interaction with American coffee. The specific compound which binds L-T4 and makes it less available for intestinal absorption is unknown, however, lipid sequestration may be a possible mechanism, as lipid content makes up 15–17% of arabica coffee and 10–11.5% of robusta coffee.

The increase in TSH, which occurred during routine coffee consumption, and then the subsequent decrease in TSH after cessation of coffee and concomitant L-T4 indicates that in this case, it is likely that coffee was the compound that caused the interaction; there are no known drug interactions with the patient’s other medications. Also, no known interactions have been reported with caffeine, creamer, or sugar.  It is also important to note that increasing the dose of L-T4 in this patient may have caused harm in the future had the patient ceased drinking coffee with her medication, indicating the importance of assessing coffee consumption in a patient taking L-T4, especially in patients with nonsuppressed TSH.

The authors conclude by stating that “coffee should be uniformly added to the list of compounds that may decrease L-T4 absorption across drug compendia.”

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1. Wegrzyn, N.M. Malabsorption of L-T4 Due to Drip Coffee: A Case Report Using Predictors of Causation. Journal of the Academy of Nutrition and Dietetics.