|Ahead of print publication
A case of acute liver injury induced by methimazole
Karthika Niveditha1, Arun S Menon1, Harish Kumar1, Malini Eapen2, Rajesh Gopalakrishna3
1 Department of Endocrinology, Amrita Institute of Medical Sciences, Kochi, Kerala, India
2 Department of Pathology, Amrita Institute of Medical Sciences, Kochi, Kerala, India
3 Department of Gastroenterology, Amrita Institute of Medical Sciences, Kochi, Kerala, India
|Date of Submission||13-Dec-2020|
|Date of Acceptance||14-Dec-2020|
|Date of Web Publication||19-Apr-2021|
Arun S Menon,
Department of Endocrinology, Amrita Institute of Medical sciences, Kochi, Kerala
Source of Support: None, Conflict of Interest: None
Antithyroid drugs, methimazole, and propylthiouracil have been reported to cause hepatotoxicity. We report the case of a patient with methimazole induced liver injury who presented within a few weeks of commencement of the drug. She presented with a cholestatic picture and responded well to discontinuation of the drug and administration of steroids.
Keywords: Cholestatic jaundice, hyperthyroidism, methimazole
|How to cite this URL:|
Niveditha K, Menon AS, Kumar H, Eapen M, Gopalakrishna R. A case of acute liver injury induced by methimazole. Thyroid Res Pract [Epub ahead of print] [cited 2021 Jun 22]. Available from: https://www.thetrp.net/preprintarticle.asp?id=314051
Antithyroid drugs, methimazole, and propylthiouracil have been reported to cause hepatotoxicity. Methimazole rarely causes cholestatic jaundice, which can be a management challenge when it occurs. We report a case of methimazole induced cholestatic jaundice which was successfully treated.
| Introduction|| |
A 60-year-old female was referred with complaints of yellowish discoloration of sclera, dark urine, and pruritus of 2 weeks duration. She had been diagnosed to have hyperthyroidism 1 month prior and commenced on methimazole 20 mg twice daily. She had loss of appetite but no abdominal pain, distension, fever, bleeding diathesis, altered sensorium, or fever. Her body weight was 54 kg and height 164 cm was noted. She had a heart rate of 110 beats/min and blood pressure of 140/90 mmHg. Physical examination revealed scleral icterus and multiple pruritic scratch marks over the body. There was no palpable goiter. Her clinical activity score was 2/7. Her laboratory investigation showed that free thyroxine level was 1.36 ng/dl (1–1.6 ng/dl), thyroid-stimulating hormone was 0.02 IU/ml (0.25–4.00 IU/ml), anti-TPO was 387 (0–34 U/ml), and T3 was 4.18 (2.3–4.2 pg/ml). Her total bilirubin was elevated at (12.21 mg/dl), direct bilirubin (8.0 mg/dl), serum aspartate aminotransferase (45 IU/l), serum alanine aminotransferase (97 IU/L), serum alkaline phosphatase of 258 U/L, and GGT was 62 U/L. Serum albumin was 4.1 g/dl, and coagulation profile was normal. Viral hepatitis was excluded by serological analyses. To rule out autoimmune liver diseases, Anti mitochondrial antibody (AMA) and ANA were sent. AMA was negative but ANA was positive (speckled pattern, 2+) cANCA and pANCA were negative. Serum iron, ceruloplasmin, Alpha fetoprotein (AFP), and Carcinoembryonic antigen (CEA) were normal. Abdominal ultrasound showed normal liver span, no biliary obstruction, and no focal hepatic lesion.
| Case Report|| |
She was suspected to have cholestatic liver disease due to methimazole. The drug was withheld and the patient was started on oral lithium 300 mg BD and propranalol 20 mg BD. Magnetic resonance cholangiopancreatography (MRCP) showed no Intrahepatic biliary radicle dilatation (IHBRD) and Common Bile duct (CBD) dilatation, no enhancing lesion in CBD or periampullary region. As the patient had ANA positivity, to rule out other autoimmune diseases involving liver biopsy was performed that showed canalicular cholestasis with focal lobular and portal inflammation with eosinophils, possibly drug-induced liver injury [Figure 1]. Dexamethasone 1 mg TID was started for the management of methimazole-induced hepatic injury. As the free T4 levels started to rise in spite of lithium treatment, the patient underwent low dose radioiodine ablation with 7.9 Mci dose of oral I131 sodium iodide solution with steroid cover. The liver function tests all normalized over the next 6 weeks. She developed hypothyroidism 6 months after administering radioiodine and currently is on thyroxine replacement.
|Figure 1: (a and b) (X400) – Shows portal inflammation with a component of eosinophils and lobular changes with canalicular cholestasis and mixed inflammation respectively|
Click here to view
Antithyroid drugs are thioamide derivatives that are in use for more than 60 years for managing hyperthyroid patients. Methimazole and propylthiouracil (PTU) are two frequently used antithyroid agents to treat hyperthyroidism. Despite being effective agents in controlling hyperthyroidism, rarely their administration is associated with hepatotoxicity. Methimazole-induced hepatotoxicity usually develops in the first few weeks of drug consumption with an estimated incidence of 0.1%–0.2%, compared to PTU where the toxicity develops in the first 3 months. Methimazole-induced hepatotoxicity is typically a cholestatic process. There are numerous factors that can contribute to differences among individuals in their sensitivity to xenobiotics. Methimazole metabolism through CYP450 enzymes gives N-methylthiourea and glyoxal as two major metabolites. N-methylthiourea is further oxidized with flavin-containing monooxygenase (FMO) enzyme to give sulfinic and sulfenic acid species. N-methylthiourea is proposed to be the main methimazole reactive metabolite responsible for the hepatotoxicity induced by this drug. Glyoxal is a reactive compound capable of interacting with different intracellular targets, such as proteins and sulfenic acids are high electrophilic species that form irreversible adduct with cellular nucleophilic sites and may have a role in methimazole-induced hepatotoxicity. Polymorphism in drug-metabolizing enzymes also has a role in the idiosyncratic nature of the hepatic injury. The critical role of cellular defense mechanisms such as glutathione (GSH) in preventing antithyroid drugs-induced hepatotoxicity is also important,, but the liver GSH content might be variable in different situations. Liver GSH reservoirs are lower in malnourished patients and/or in such as alcoholism, so it seems that the risk of methimazole hepatotoxicity might be highest in these situations. Hence, particular attention should be given to the possibility that unexpected toxic reactions may be encountered under conditions of tissue GSH depletion. Physicians might advise their patient to avoiding alcohol consumption during anti-thyroid therapy. Next is the cytokines which are thought to play a role in immune-mediated liver injury caused by methimazole.
| Discussion|| |
Another mechanism is that the activity of different enzymes which are involved in the antioxidant defense mechanism of the liver are changed in hyperthyroidism. Studies have showed that glutathione reductase (GR) activity was lower in hyperthyroid patients, and they have impaired antioxidant defense mechanism.,,, The hypothesis that GD itself has a role in antithyroid drugs-induced hepatic injury needs more controlled and in-depth investigations to be clarified. Patients should be aware of symptoms which might indicate anti-thyroid drugs-induced hepatic injury. Indeed, all anti-thyroid taking patients should be trained to report symptoms such as abdominal discomfort and pain, especially in the upper right quadrant and also other signs such as urine discoloration, which are connected to serious adverse reactions such as hepatotoxicity.
Intravascular glutathione was founded to be an effective treatment in the case of methimazole-induced hepatotoxicity and lowered transaminase levels in one patient. In another study by Becker et al., it has been reported that corticosteroids might alleviate methimazole-induced hepatitis. Prednisolone administration also has been shown to rapidly help recovery of patients from jaundice induced by anti-thyroid medications.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that her name and initial will not be published, and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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