Endocrine Abstracts

Introduction: Refractory hypothyroidism is defined by clinical or biochemical signs of hypothyroidism (serum TSH level >4.5 mU/l after an interval of six weeks after the last dose increase), despite increasing levothyroxine (LVT) doses beyond 2.5 μg/kg per day.

Observation: A 67-year-old female patient, followed for a 1 mm NIFT-P classified as pT1a, low risk, initially put on LVT 150 mg/day, presented with hypothyroidism, clinically with asthenia, constipation, and biologically with a TSHus of 145 mUI/l, despite titration of LVT up to 1 mg/day (i.e, 4.1 mg/kg/day), liothyronine sodium 0.1 mg/day and dexamethasone 1 mg/day. The patient reports good therapeutic compliance, with good levothyroxine conservation. She does not report signs of malabsorption.

Methods: The patient was hospitalized in the endocrinology and metabolic diseases department for a 5-days levothyroxine absorption test. The principle consists of supervised administration of LVT on an empty stomach with monitoring the patient 1h after the ingestion. TSHus and FT4 blood samples were taken before LVT administration in 1st day of the test and 2h after administration in 5th day of the test.

Results: On the first day, TSHus before LVT administration was 91 mIU/l (0.25-5), with FT4 at 0.3 ng/dl (0.7-1.5). Then, on the 5th day, TSHus 2 hours after administration was 40.27 mIU/l (0.25-5), and FT4 was normal at 20.5 pmol/l (10-28.2). The patient was subsequently, switched to LVT tablets (due to the high cost of liquid LVT). A thyroid function test was repeated after 5 days, showing normalization of TSHus at 1.39 mIU/l (0.25-5), and FT4 at 20.4 pmol/l (10-28.2). In addition, a malabsorption check-up was revealed intestinal amebiasis of the Entamoeba histolytica histolytica, treated with a negative control work-up. Associated with a Helicobacter pylori chronic gastritis under treatment.

Conclusions: The 5-days LVT absorption test allowed the diagnosis of pseudomalabsorption in this patient, given the normalization of the thyroid function test, despite the presence of Helicobacter pylori gastritis.