Severe Refractory Hypothyroidism in a 48-Year-Old Female: Role of Lowdose Thyroxine Absorption Test in Establishing Diagnosis of Noncompliance

A 48-year-old female presented with severe chronic hypothyroidism despite progressively increasing doses of levothyroxine. Poor adherence was suspected based on previous laboratory investigations. A low dose thyroxine absorption test using 400 µg of levothyroxine taken orally was performed. FT4 increased by 4.7 pmol/L at 3 hours and 6.6 pmol/L at 5 hours, following ingestion, effectively ruling out malabsorption. Her cardiac hemodynamic profile, measured noninvasively, also improved following levothyroxine intake, further supporting our diagnosis. Poor adherence was successfully managed by implementing twice weekly visits by a registered nurse and an improvement in both thyroid function tests and cardiac parameters was seen at the one-month follow-up visit. We suggest using a lower dose thyroxine absorption test, owing to its efficacy in establishing diagnosis and a safer alternative compared to higher doses in particular in high-risk cardiac patients.