SUN-590 Failure to Control Severe Hypothyroidism with L-Thyroxine Tablets Corrected by Switching to Oral Soft Gel Formulation

Background: Oral tablets of levothyroxine (L-T4) are the standard of care for the treatment of Hypothyroidism and are recommended by current professional guidelines. However, patients with malabsorption syndromes, intolerance to excipients or dyes in tablets, or the intake of certain medications or foods may not be adequately controlled on these tablets. The use of liquid soft gel capsules (Tirosint) has been reported to be of value in such circumstances. Case Report: A 29 year old woman underwent total thyroidectomy followed by 124.5 mCi (131)I therapy at another facility for a right sided 3.7cm PTC with tall cell features. 12 ipsilateral central nodes were positive for cancer. Post therapy WBS was negative for evidence of distant metastases. She was placed onto branded L-T4 treatment but over the next 2 years, in spite of carefully documented adherence to her medication regimen, and with daily doses increasing from 0.1 to 0.3mg, TSH levels were unstable varying from 0.03 to 3.13μIU/ml and then 3 months later rose progressively further to 130μIU/ml. Her clinical Hypothyroidism became critical requiring emergent use of IV L-Thyroxine by her physicians who added L-T3 20μ/d to her L-T4 0.3mg but her TSH did not go below 98.54. She sought care at our institution. Issues of proper technique of medication administration were explained and emphasized with which the patient insisted she was fully compliant. Nevertheless, and in spite of a further increase in the daily L-T4 dose to 0.35mg, TSH remained excessive at 86.94. Treatment was then changed to Tirosint soft gel capsules alone starting at 0.3mg and then decreasing progressively to 0.2mg daily as her TSH reduced to 4.39 (6 months) and has remained in the range of 0.011 to 0.057 over the next 3 years. Other than Vitamin D and the temporary use of Depo-Provera, the patient denied the use of any other medications or supplements. Discussion: L-T4 tablets have long been the preferred and recommended treatment form for Hypothyroidism by professional societies. (1, 2) However, reports have appeared noting poor and inconstant response to this treatment in occasional patients such as those with malabsorption syndromes such as following bariatric surgery (3) or with gastroparesis (4), or with the concomitant intake of other medications such as proton pump inhibitors (5) or foods such as coffee (6). In such circumstances, it has been reported that use of liquid L-T4 or liquid soft gel capsules containing no excipients beyond glycerin and gelatin results in improved absorption of L-T4 with better and more stable control of thyroid biochemistry including TSH. (3, 4, 5, 6, 7) We present a case of a patient with Papillary Thyroid Cancer who, following total thyroidectomy and (131)I therapy, had variable and inadequate TSH suppression with development of clinical unresponsiveness to standard branded L-T4 treatment. Switching therapy to a soft gel product has enabled stable control of TSH