Endocrine Abstracts

Introduction: Refractory hypothyroidism is a fairly common situation in the practice of any endocrinologist, being defined by the persistence of hypothyroidism despite adequate doses of replacement therapy with Levothyroxine, generally supraphysiological. We report the case of refractory hypothyroidism under high doses of Levothyroxine.

Observation: she was a 54-year-old woman, diabetic Type2, followed for 06 years for papillary carcinoma of the thyroid gland, for which it was operated and irradiated, currently in clinical, biological and morphological remission. she was already under 325 μg/day of levothyroxine taken orally, or 4 μg/kg/day, for a target of TSH between 0.1 and 0.5, by the way as a TSH suppressant treatment. The patient recognizes having a regular pace of taking his medication without omission or errors related to the schedule of her medication. On examination, she shows symptoms of hypothyroidism, asthenia and pallor, with infiltration of the face and integuments. Biology revealed a TSH=30 IU/ml, and FT4 at 0.58ng/dL (usual values between 0.7 and 1.5). An oral thyroid hormone absorption test was performed, at a dose of 1000 μg in a single dose on an empty stomach, under strict medical supervision. The FT4 assay was performed at times 0, 1h, 2h, 3h, and at 24h after intake. The results showed the absence of elevation of FT4, which is in favor of malabsorption. After elimination of the obvious causes, a malabsorption assessment was requested and returned without anomalies: the total cholesterol level at 1.8 g/l, ferretinemia at 77 mg/l, calcium phosphorus and vitamins B9 and B12 normal. A serology of celiac disease, anti-parietal antibodies, and digestive fibroscopy were requested. This finally led to the diagnosis of autoimmune gastritis, considered the cause of the malabsorption of levothyroxin. The patient was put under levothyroxine in the form of soft capsules and has marked a good evolution.

Conclusion: Our observation illustrates the interest of the thyroid hormone absorption test, a key examination to distinguish between true malabsorption and pseudo-malabsorption. This load test must lead to an etiological assessment in search of an organic cause for the malabsorption.