Has anyone else had problems taking allopurinol along side their post thyroidectomy thyroid hormone replacement therapy (either T4 or combination therapy)?
I have a background of Thyroidectomy (PCT) and Follicular Lymphoma. As a result of the FL I have high uric acid levels leading to gout and joint erosion, so my rheumatologist prescribed Allopurinol 100mg, then 200mg, then supposedly 300mg. I never got to 300mg - I stopped because a ramping up of hypo symptoms led me to suspected that it was having an adverse effect on my hormones.
I have now had two attempts at being on allopurinol, first when I was on T4 monotherapy (which did not suit me) and then I gave it a second chance after I was stable NDT (which is lovely by the way). Both times I was met with an extreme ramping up of hypo symptoms.
I've looked into it and it seems that Allopurinol suppresses fT4 and fT3 levels (but not total hormone levels), along with other hormones such as cortisol and testosterone. It also increases TSH. (see links blow).
It surprises me because I would have thought that if Allopurinol were having an adverse effect on thyroid hormone levels, it would be on production. So being on replacement therapy it should not be a problem. Right? But it seems that there is an effect, and it is a strong one. So the effect must be on the availability of the hormones. Perhaps because of increased clearance. None of the papers I have found have offered an explanation.
As you had no answers, I had a look to see if I could find anything. And I did - albeit very little appears to have been published.
This study appears to support your suggestion there is an effect.
Observational Study
Rheumatol Int
. 2015 Nov;35(11):1857-61.
doi: 10.1007/s00296-015-3355-5. Epub 2015 Sep 5.
Increase in thyroid stimulating hormone levels in patients with gout treated with inhibitors of xanthine oxidoreductase
Fernando Perez-Ruiz 1 , Sandra Pamela Chinchilla 2 , Joana Atxotegi 3 , Irati Urionagüena 2 , Ana Maria Herrero-Beites 4 , Maria Angeles Aniel-Quiroga 5
Affiliations
PMID: 26342297 DOI: 10.1007/s00296-015-3355-5
Abstract
Increase in thyroid stimulating hormone (TSH) levels over the upper normal limit has been reported in a small percentage of patients treated with febuxostat in clinical trials, but a mechanistic explanation is not yet available. In an observational parallel longitudinal cohort study, we evaluated changes in TSH levels in patients with gout at baseline and during urate-lowering treatment with febuxostat. Patients to be started on allopurinol who had a measurement of TSH in the 6-month period prior to baseline evaluation were used for comparison. TSH levels and change in TSH levels at 12-month follow-up were compared between groups. Patients with abnormal TSH levels or previous thyroid disease or on amiodarone were not included for analysis. Eighty-eight patients treated with febuxostat and 87 with allopurinol were available for comparisons. Patients to be treated with febuxostat had higher urate levels and TSH levels, more severe gout, and poorer renal function, but were similar regarding other characteristics. A similar rise in TSH levels was observed in both groups (0.4 and 0.5 µUI/mL for febuxostat and allopurinol, respectively); at 12-mo, 7/88 (7.9 %) of patients on febuxostat and 4/87 (3.4 %) of patients on allopurinol showed TSH levels over 0.5 µUI/mL. Doses prescribed (corrected for estimated glomerular filtration rate in the case if patients on allopurinol) and baseline TSH levels were determinants of TSH levels at 12-month follow-up. No impact on free T4 (fT4) levels was observed. Febuxostat, but also allopurinol, increased TSH levels in a dose-dependent way, thus suggesting rather a class effect than a drug effect, but with no apparent impact on either clinical or fT4 levels.
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