U018
Management of Radioiodine-Induced Refractory Hypothyroidism
T Htay, H Yap, V Lecamwasam, K Baynes; Ealing Hospital.
A 33 year Asian woman, treated with radioiodine for relapsed Graves thyrotoxicosis in October 2013, developed profound hypothyroidism three months after treatment. Levothyroxine 75 microgram daily was commenced. However, after 2 months of treatment, she remained symptomatic and TFT showed no improvement. Adherence to treatment including taking medication on an empty stomach was reiterated. She reported full concordance and was not using any medicine to interfere with absorption. She had no symptoms of malabsorption and coeliac screen was negative.
Despite increasing Levothyroxine dose to 200 microgram daily, her biochemical and clinical status was unchanged. We felt that non-concordance might be her underlying issue. Hence, her conventional daily regimen was altered to direct observation intermittent dosing. She was started Levothyroxine 700 microgram twice per week in the ambulatory care unit. Her biochemical improvement with this regimen excluded Levothyroxine malabsorption. However, euthyroid state was still not achieved. As we had concerns about the potential for serious physical deterioration with prolonged severe hypothyroidism, she was admitted as an in-patient for one week. She was switched back to Levothyroxine 200 microgram daily under close supervision resulting in biochemical hyperthyroidism. During this admission, she had a psychiatric assessment which found low mood, but no psychiatric illness requiring further psychiatric input. She blamed excessive tea drinking for affecting absorption and she abstained. She is now well, able to work and on Levothyroxine 100 microgram daily has evidence of slight over-replacement
Table: TFT status during various Levothyroxine treatment regimens
|
|
After RAI |
Thy 75µg OD |
Thy 200 µg OD |
Thyroxine 700 µg twice week |
Thy 400 µg twice week |
Thy 200 µg OD |
Thy 100 µg OD |
|
TSH mIU/L |
>100 |
>100 |
>100 |
>100 |
56.4 |
0.833 |
0.08 |
|
FT4 pmol/l |
2,74 |
3.47 |
4.71 |
7.53 |
14 |
41.54 |
27.2 |
Discussion: This case illustrates that if daily treatment with Levothyroxine does not achieve the target therauptic range in hypothyroidism, concordance, interfering drugs causing decreased absorption, and undiagnosed malabsorption disorders should be considered as the cause (1). Direct observation of Levothyroxine treatment is an alternative therapeutic option, which can be used in difficult cases and has some evidence for efficacy and clinical safety (2).
(2) Grebe SK, Cooke RR, Ford HC, Fagerstrom JN, Cordwell DP, Lever NA, Purdie GL, Feek CM 1997. Treatment of hypothyroidism with once weekly thyroxine. J Clin Endocrinol Metab 82:870–875