Challenges of treating thyroid disease: the need for a revisit

We applaud Varughese et al. on their Grand Round (JRSM, November 2006) highlighting the caveats to be exercised from a practical perspective, when managing patients with hypothyroidism on levothyroxine replacement. ¹ Their comprehensive discussion serves to remind clinicians of the intricacies in the management of hypothyroidism and the potential cautions to be remembered in such circumstances.

In this context it would be worth noting that tablet formulation of levothyroxine has also been demonstrated to be absorbed less well than powdered levothyroxine, ² and interestingly the degradation of tablet based formulations of levothyroxine with preservative have been reported to occur faster in contrast to oral liquid formulation of levothyroxine 25 mg/mL compounded from crushed tablets. ³

The controversial issues in the management of thyroid disease are crucial for both primary and secondary care clinicians. ⁴ Indeed, in some situations the timing of treatment in patients with hyperthyroidism is also equally important and should be explored in detail. ⁵ As an illustrative example, the same authors had reported on a patient with end stage renal disease on haemodialysis who developed hyperthyroidism. ⁵ Despite titrating the dose of treatment, carbimazole therapy in the setting of haemodialysis had been suggested to be less efficacious due to the fact that the conversion of carbimazole to its active form (methimazole) is inhibited in an acidic environment; it is of note that methimazole is not protein bound and is therefore dialysed. ⁵ Propylthiouracil, another antithyroid agent, is protein bound and would not get dialysed in such patients. ⁵ A high index of suspicion is required in such clinical scenarios and as Varughese et al. emphasize in their Grand Round, the possibility of other causes should be further explored before patient compliance is doubted.