The Use of Levothyroxine Absorption Tests in Clinical Practice

Refractory hypothyroidism in children: an overview

Refractory hypothyroidism (RF) defined as raised serum levels of thyroid stimulating hormone (TSH) above upper limit of the reference range with or without the persistence of hypothyroid symptoms following a 6-week interval after the dosage was last increased to upper limits of dose per age. The most common cause of RH is inadequate compliance. In addition, diet, concomitant medication interactions, and gastrointestinal diseases can all result in l-thyroxine (LT4) malabsorption, which can cause RH. Moreover, weight gain, switching brands of LT4, poor storage of LT4, chronic liver disorders, cystic fibrosis, nephrotic syndrome, consumptive hypothyroidism, Addison's disease are significant contributors to RF in children. RH in children is frequently asymptomatic, when symptoms do occur, they are typically minor and resemble those of hypothyroidism. It is essential to identify RH early and treat its underlying cause in order to avoid overusing LT4, which can lead to cardiac and bone problems. Endocrinologists should handle children who they suspect of having RH methodically after making sure there is enough compliance. Searching for undiagnosed illnesses and/or other factors that can affect LT4 absorption could be part of this. We present this review after an extensive literature search and long-standing clinical experience. This review's objective is to shed light on the causes, clinical manifestations, investigations, and treatment of RH in children.

Levothyroxine liquid oral substitution as an alternative treatment for refractory hypothyroidism due to gastrointestinal malabsorption: A case report

Tablets of levothyroxine (LT4) are the most used form for the treatment of hypothyroidism. Some patients may present with refractory hypothyroidism despite a high daily LT4 dose. We report the case of a 49-year-old woman who was admitted to our department for refractory hypothyroidism. She was treated with 300 μg oral LT4 tablets daily (3.9 μg/kg/day). Despite good compliance and regular intake of high doses of LT4, she had persistent symptoms of hypothyroidism and a thyroid-stimulating hormone level of 92.4 mIU/L. LT4 absorption test was consistent with the diagnosis of malabsorption. Etiological investigations revealed Helicobacter pylori gastritis. Helicobacter infection was adequately treated, but symptoms of hypothyroidism and elevated thyroid-stimulating hormone persisted. Increased LT4 doses (400 μg) failed to normalize thyroid-stimulating hormone levels. Thus, she was put on LT4 liquid form at a dose of 80 drops/day per day (400 µg). Two weeks later, she presented with clinical and biological improvement with a normal free thyroxine level of 1.14 ng/dL. Patients with gastrointestinal disorders may present with refractory hypothyroidism despite increasing doses of LT4. Switching to liquid formulation may resolve this problem.