Importance of the Levothyroxine Absorption Test in an Adolescent Girl

Abstract

Hypothyroidism is a commonly encountered problem in daily clinical practice. Although the management of hypothyroidism may seem straightforward, it can become challenging when patients’ Thyroid-Stimulating Hormone (TSH) values remain elevated despite treatment. Various factors, including non-adherence and malabsorption, can contribute to this issue. Consequently, it is crucial to identify the underlying cause of increased levothyroxine demand, as this will prevent unnecessary dosage adjustments of levothyroxine tablets. In this case, a 13-year-old girl patient, presented with a TSH level greater than 200 and an fT4 level of 0.34, along with absent secondary sexual characteristics, impaired memory, delayed puberty, easy susceptibility to anxiety, difficulty with memorisation, and poor academic performance. Despite repeated inquiries, neither she nor her mother reported any instances of non-compliance. Additionally, there were no signs suggestive of malabsorption, such as diarrhoea or oedema. Therefore, a levothyroxine absorption test was conducted to rule out pseudo-malabsorption. This test aids in distinguishing patients with non-compliance from those with true malabsorption, thereby avoiding unnecessary dosage adjustments of levothyroxine supplementation, a problem frequently encountered in day-to-day clinical practice.