Thyroxine Treatment With Softgel Capsule Formulation: Usefulness in Hypothyroid Patients Without Malabsorption

Levothyroxine sodium (LT4) is the therapy of choice for hypothyroidism. In the last decade, new LT4 formulations, such as liquid and softgel capsules, became available. Even if some evidence has been reached in the efficacy of liquid LT4 in patients with suboptimal TSH on tablet LT4, the usefulness of softgel LT4 has been rarely studied. This study aimed at evaluating the effect of switching from tablet to softgel LT4 patients without increased need for LT4. TSH was used as proxy of LT4 bioavailability and effectiveness.

During the period from April to August 2017, 19 patients on tablet LT4 treatment for hypothyroidism, mostly due to autoimmune thyroiditis, were enrolled. Subjects with causes of malabsorption or increased requirement of LT4 were previously excluded. Patients finally included were asked to switch from tablet to softgel LT4 formulation at unchanged dose and ingestion fashion (30 min before breakfast). TSH was measured with chemiluminescence immunoassays.

According to exclusion and inclusion criteria, 19 patients were finally selected. One of these had headache 4 days later and come back to tablet LT4, and 18 of them (16W/2M; mean age = 55 years; BMI 22.7 kg/m²) completed the study. They were treated with a median LT4 dose of 88 μg/day and showed a median TSH value of 3.33 mIU/L. The rate of cases with TSH ≤ 4.0 mIU/L was 61.1% (11/18 cases). When patients were re-evaluated after 3 months of softgel LT4, we observed that TSH reached levels under 4.0 mIU/L in 16/18 (88.9%) patients, TSH was lower in 11 cases, and in 6 out of 7 patients with pre-switch TSH values over the normal range. Overall, TSH values on softgel LT4 (median 1.90 mIU/L) was significantly lower from that observed during tablet LT4 (p = 0.0039).

These data show that hypothyroid patients with no proven malabsorption may have an improved TSH following 3 months from the switch from tablet to softgel LT4 preparation at unchanged dose.