From the Guidelines
Patients with Graves' disease should have regular liver function tests, especially when starting antithyroid medications, due to the potential risk of hepatotoxicity and the impact of hyperthyroidism on liver function. When managing Graves' disease, it is essential to consider the potential effects of antithyroid medications on the liver, as well as the impact of untreated hyperthyroidism on liver function. Although the provided study 1 focuses on the liver manifestations of COVID-19, it highlights the importance of monitoring liver function tests (LFTs) in patients with various conditions. In the context of Graves' disease, antithyroid medications like methimazole or propylthiouracil can cause hepatotoxicity in a small percentage of patients, making regular LFT monitoring crucial. Some key points to consider when monitoring liver function in patients with Graves' disease include:
- Obtaining baseline liver tests before starting antithyroid medication
- Monitoring LFTs every 2-4 weeks during the first three months of therapy, then periodically thereafter
- Discontinuing medication if liver enzymes exceed three times the upper limit of normal and considering alternative treatments
- Educating patients about symptoms of liver dysfunction and the importance of seeking immediate medical attention if these occur
- Considering alternative treatments, such as radioactive iodine therapy or thyroidectomy, if antithyroid medications cannot be tolerated due to liver effects.
From the Research
Liver Function Tests in Graves' Disease
- Liver function tests can be abnormal in patients with Graves' disease, with studies showing that 37% to 70.9% of patients have at least one abnormal liver function test result 2, 3.
- The most common abnormal liver function tests in Graves' disease are elevated alanine transaminase (ALT) and aspartate transaminase (AST) levels, with frequencies ranging from 26% to 52.7% 2, 3.
- Other abnormal liver function tests that can occur in Graves' disease include elevated alkaline phosphatase (ALP), gamma-glutamyltransferase (GGT), and total bilirubin (TBIL) levels 2, 3.
Factors Predicting Abnormal Liver Function Tests
- Higher free thyroxine (FT4) concentration and higher thyroid-stimulating hormone receptor antibody (TRAb) level are independent risk factors for predicting abnormal liver function tests in Graves' disease 3.
- The optimal cutoffs for FT4 and TRAb to predict abnormal liver function tests are 75 pmol/L and 15 IU/L, respectively, based on receiver operating characteristic (ROC) analysis 3.
- Older age and higher titers of TRAb may also increase the risk of liver dysfunction in Graves' disease 4.
Antithyroid Drug-Induced Liver Dysfunction
- Antithyroid drugs, such as propylthiouracil (PTU) and carbimazole (CBZ), can cause liver dysfunction in some patients with Graves' disease 5, 4.
- However, studies suggest that the elevation of liver enzymes after starting antithyroid drug therapy may not be due to the drug itself, but rather to changes in thyroid function 6.
- In some cases, liver function tests may improve after stopping antithyroid drugs, as seen in a patient who developed liver dysfunction after starting CBZ therapy 4.