Endocrine Abstracts

Young man with high BMI and known iatrogenic hypothyroidism, post radioactive iodine (RAI) treatment (2015) for Graves’ thyrotoxicosis (2011) was referred to endocrinology due to significantly raised TSH (at 50 mu/l) and low FT4 (5.0 pmol/l). He was actually admitted with progressive nausea, vomiting over last three weeks. He also complained of abnormal stool consistency (like semi-solid) intermittently. His past medical history also includes gastric bypass with gastro-jejunal anastomosis in 2015, depression and OSA. He mentioned that, since he had surgery he normally has vomit, at-least one episode every month. He was taking tab levothyroxine 200 mg daily on empty stomach and honestly mentioned he could miss the tab levothyroxine at-least twice a month. Before surgery his TSH was stable and within range but post-surgery it was fluctuating. He complained of feeling more tired and lethargic for more than 6 months. He did not have goitre and pulse rate was normal. We did a modified rapid levothyroxine absorption test while he was inpatient by giving stat dose of 1000 mg oral levothyroxine and the result (mentioned below) suggested that he was absorbing the medication well (rise in FT4 almost four times from baseline). I discussed the option of weekly and daily regimen for levothyroxine and patient opted for weekly once tab 1000 mcg.

Conclusion: A supervised rapid levothyroxine absorption test can assist in diagnosis of pseudo-malabsorption and safe time and resources. A rise in FT4 of 2.5 times or more can convincingly rule out any malabsorption disorders.