There are two basic medications that can be used to control Graves’ disease and bring thyroid levels into the normal range. The first and safest of those is propranolol. This beta blocker does an excellent job of controlling abnormal heart rates. Patients with Graves’ disease whose heart rate exceeds 90 beats per minute typically would benefit from beta blocker treatment. Propranolol is a very safe medication and has been used for quite a long time. This may not be appropriate for patients with coexistence cardiovascular disease and consultation with your physician on an individual case is always necessary. Patients with high heart rates typically see dramatic symptomatic improvement with the initiation of beta blocker treatment.
Anti-Thyroid Drugs (ATD’s)
The other option is antithyroid medications. These come in two forms, either methimazole (Tapazole) or propylthiouracil (PTU). Of the two of these, methimazole is used most commonly because it is the safest of the two medications. Typically, methimazole is used in combination with beta blocker treatment. Patients taking beta blockers tend to have lower heart rates, less shortness of breath and less fatigue than patients who are on methimazole alone. In 2015, the American Thyroid Association issued new guidelines for hyperthyroidism and recommended an antithyroid medication such as methimazole be prescribed for a 12-18 month period. This allows for evaluation and identification of those patients who will spontaneously resolve and need no further treatment. In fact, there has been a dramatic increase in use of antithyroid medications for the treatment of Graves’ disease over the last decade.
Side Effects of ATD’s
While methimazole is frequently used, it does have some potential side effects which can limit its usage. Patients frequently have stomach upset with this medication; this will typically get better after they have been on it for a few weeks. The downside to methimazole therapy is that it can have some serious side effects. These do not happen very often but still should be considered. Minor side effects include a rash, itching, jaundice, change in color of the stools, joint pain, abdominal pain, nausea, fatigue, fever and sore throat.
Serious Possible Side Effects of ATD’s
Major or serious side effects can include a suppression of the immune system called agranulocytosis (aka aplastic anemia). This happens in 0.7% of patients but is a very serious complication. Any febrile illness with high fevers should be evaluated for this possibility for patients who are on these medications. Rarely a vasculitis or a drug-induced lupus-like syndrome can occur. Liver damage can occur in 3-4% of patients including a small risk of complete liver failure. Thankfully, this devastating complication is seen in 0.03% of the patients on methimazole. While most people can tolerate methimazole, 17-19% of patients discontinue this medication because of adverse side effects. Even less well tolerated is PTU where we see about a third of patients discontinue because of unwanted side effects.
ATD’s Require Careful Monitoring!
When patients are started on methimazole or PTU, a baseline blood test is recommended. Low white blood cell counts are common in Graves’ disease, as are abnormal liver enzymes. So, it is important to establish a baseline to be used for comparison to make sure that the medication is not making these situations worse. Once on medications, free T4 and T3 should be checked about every six weeks after initiation of therapy. It is not uncommon that it takes more methimazole to bring a patient under control than it does to maintain once adequate control is achieved. Typically, we recommend testing every four to six weeks until a stable dose is established on these medications.
Warning! A differential white blood cell count (CBC) should be obtained any time there is a febrile illness or at the onset of a sore throat. Should a patient develop these types of illness and seek care at an urgent care center, it is important to let them know that you are on these medications and that there is a risk of immune suppression that needs to be evaluated during any of these types of illness. Liver function should be evaluated routinely to make sure there is hepatocellular integrity and no side effects from the medications. This should also be checked when there is an appearance of a rash, jaundice, light colored stool or dark urine. Joint pain, abdominal pain, bloating, anorexia, nausea or fatigue are also good reasons to check liver function for patients who are on antithyroid medications.
How Long Will ATD Therapy Last?
The duration of therapy with these medications should be discussed in light of antibody levels. Declining antibodies can be a good sign that Grave’s may resolve spontaneously. On the other hand, persistently high antibody levels typically mean that Grave’s is not going to resolve without definitive therapy. Options for definitive Grave’s therapy options are discussed here.