Endocrine Abstracts

Introduction: In the treatment of amiodarone-induced type I or mixed thyrotoxicosis, sodium or potassium perchlorate is often associated to thionamides, when the latter are insufficient for a prompt control of thyroid hormone secretion. Perchlorate competes with iodine for entrance into the follicular cell, and also induces a discharge of iodine from these cells with each administration. We compare the effect of 3 different regimes of perchlorate with methimazole on control of fT4 secretion.

Methods: Retrospective. 41 patients were treated by Endocrinology of a tertiary hospital for amiodarone –induced thyrotoxicosis (AIT) with potassium/sodium perchlorate associated to methimazole (30 mg/day) over an 11-year period. Diagnosis of type I or mixed AIT was based on thyroid doppler ultrasound, fT3/fT4 ratio, MIBI scan, IL-6 levels, and response to therapy. Patients with mixed AIT initiated perchlorate following inadequate response to glucocorticoid therapy and/or methimazole. Patients with suspected type I initiated treatment with methimazole alone or combined with perchlorate. 3 perchlorate regimes were used: Group I: 150 mg 6 × /day, Group II: 200 mg 5 × /day, Group III: 300 mg tid, maximum of 6–8 weeks. Response was compared, analyzing the number of days necessary for initiation of a sustained fT4 descent (minimum initial descent: 2 pg/ml). [Interquartile range].

Results: 26 (63.4%) men, mean age 73 (s.d.:11.7). Type I AIT: 9/41 (22%), mixed: 31/41 (75.6%), Type II 1/41 (2.4%). 5 patients were not included in the analysis: 1 patient receiving 100 mg 4 × /day, 1 who did not take medication, 1 initially on expired perchlorate, 1 non-responder until switched from propylthiouracil to methimazole, 1 lost to follow-up. The response rate of the remaining patients was analyzed: 10 (27.7%) in Group I, 21 (58.3%) in Group II, and 5 (13.9%) in Group III.

Median baseline fT4 was 39.3 pg/ml [30.1–45.2], 24.2 [20–40.5), and 34.5 [20.4–41] in Groups I, II, and III respectively. Median duration of perchlorate therapy was 42 days [23–45]. Median number of days for response was significantly different among groups, with 3 [2–6], 7 [4–12], and 7 [4–25] in group I, II and III respectively, P = 0.015. No significant side effects were observed.

Conclusions: The frequency of perchlorate administration could perhaps play a role in response time in amiodarone-induced type I and mixed thyrotoxicosis, with a more prompt response when perchlorate is administered more often. These results indicate a need for prospective trials, with larger number of patients, designed to compare the effect of different perchlorate regimes.