#1707496 Levothyroxine Absorption Test: A Limitation in the Diagnosis of Delayed Absorption

The oral levothyroxine absorption test is an infrequently used test that measures intestinal absorption of free T4 to diagnose malabsorption as the cause of persistent, uncontrolled hypothyroidism. We present a case of a patient with a positive result of a 1000 mcg levothyroxine test at 2 hours, indicating malabsorption, who was then later found to have a normal response at 16 hours, calling into question the positive predictive value of the test.