Endocrine Abstracts

Introduction: Hypothyroidism is considered refractory to oral levothyroxine substitution, when there is biochemical (serum level of TSH (thyroid stimulating hormone) above the upper target level) or clinical evidence of hypothyroidism, despite increasing dosages of oral levothyroxine beyond 2.5 μg/kg daily. In these circumstances, further increments in the dosage of levothyroxine may not always be the most appropriate intervention. In such a situation, physicians need to search for causes of decreased absorption of levothyroxine or increased demand for thyroxin and the solution.

Case report: We present the case of a 55-year-old woman who underwent total thyroidectomy for multinodular goiter, then ablative treatment with 30 mci of radioactive iodine 131, after postoperative biopsy resulted in papillary thyroid cancer. She then started treatment with the levothyroxine replacement dose. In control after 6 weeks of treatment with levothyroxine, TSH level was high and her complaints related to hypothyroidism. We gradually increased the dose of levothyroxine after each periodic TSH test, reaching more than 300 mg of levothyroxine/day, but the TSH level remained high. We searched for the cause of refractory hypothyroidism, but found neither poor compliance nor malabsorption. In our case where it was necessary and urgent to inhibit TSH, following the protocol of differentiated thyroid cancer to control the progression of papillary thyroid cancer, we tried combination therapy with T4 (Thyroxin) and T3(triiodothyronine), and in the next control TSH decreased. We adjusted the T4/T3 doses gradually and after a few checks, the desired TSH levels were reached and the patient felt clinically well.

Conclusion: Whilst current guidelines do not suggest routine use of combination T4/T3 therapy, they do acknowledge a trial in patients with refractory hypothyroidism to levothyroxine treatment, may be appropriate. Our case confirms that.