SUN-587 Oral Liothyronine (LT3) May Be Better Absorbed Compared to LT4 Tablets after Biliopancreatic Diversion Surgery

Introduction: Levothyroxine (LT4) is the mainstay of treating hypothyroidism patients. Increased levothyroxine requirements are expected after bariatric surgery and small bowel diseases. There have been studies showing treatment of resistant hypothyroidism following bariatric surgery with soft gel or liquid form of LT4. Here we report a case of biliopancreatic diversion in which thyroid hormone replacement could not be done with LT4. However, treatment with Liothyronine (LT3) was successful. The Case: 57 year old Caucasian male with history of gastric bypass surgery for morbid obesity in 2009, chronic pain, cauda equine syndrome, iron deficiency anemia due to poor gastric absorption after gastric bypass surgery, on IV iron, and post ablative hypothyroidism since 1993 who presented to the VA endocrinology clinic for hypothyroidism. He had been controlled on thyroid replacement with LT4 tablets since 1993 up until he had biliopancreatic diversion with duodenal switch in Oct 2009. He was seen at the VA endocrinology clinic first in March 2016. Outside records indicated that TSH was high between 2009-2016. He claimed compliance on thyroxine PO at 300 mcg daily. From March 2016 until May 2018, LT4 dose was increased gradually to 875 mcg in am with water. In March 2018 TSH was 44.95 µIU/ml, free T4 0.92 ng/dL, and total T3 62.39 ng/dL and the albumin level was 4.1 g/dL. TSH level decreased to 17 µIU/mL in June 2018 after levothyroxine dose was increased to 875 mcg in May 2018. Since liquid or soft gel forms are non-formulary at the VA, he was treated with Liothyronine PO at 50 mcg daily. TSH level in October 2018 was 0.05 µIU/mL, fT4 was 1.77 ng/dL, and total T3 146.4 ng/dL. Conclusion: Biliopancreatic diversion can severely affect LT4 absorption. LT3 may have better bioavailability than LT4 tablets after bariatric surgery.