There's a risk to the liver seen in higher doses such as 20 mg and more. However as time goes by and the MMI begins to work, doses requirements drop. Maintenance doses are usually 5 mg and less.

{{{hugs}}}

Elevated liver enzymes have many causes.

Please continue on to the next page, on this link, for the more common medications that cause liver problems.
http://www.medicinenet.com/liver_blood_tests/page3.htm

Undiagnosed hyperthyroidism often causes elevated liver enzymes. When first treating it's not unusual to see these liver enzymes climb a bit more, before the body has had a chance to come to normal thyroid levels, and the liver to begin to function normally, and begin to heal.

We need a normal metabolism to allow the liver to function well. When patients on ATDs are over dosed and their thyroid levels drop too far, the slowed metabolism causes the liver to struggle filtering everything..including the overdose, plus any other medications they may be taking. The potential overdose of either ATD is the major problem here. That and not allowing enough time to pass once the metabolism has returned to closer to normal, and the body to begin healing.

Problems patients face with both ATDs and their liver have multiple causes.

Doctors that don't realize how powerful these drugs are and prescribe excessive amounts of he drugs.

Non-compliant patients. Continuing hyper simply allow the existing problem to get worse.

Doctors that expect a Graves' patient to have a TSH response as the more common Hashimotos's patient will have. we are only one percent of thyroid patients and our antibodies work in place of TSH.

Failure to split the doses in new patients, causing low, then high thyroid levels during each 24 hour period. When this happens while still on a high ATD dose, the liver again is getting a double punch.
Because of either non-compliance or poor prescribing practice, MMI has a safer track record, because the half life is longer, thus the over dose is spread out through the 24 hour period.

PTU has a half life of 75 minutes. When prescribed at either once or twice a day, instead of the required 3 doses each eight hours, the patient is sent hypo starting at about 1 hour after the dose is taken. The metabolism is slowed to almost a halt. The liver then receives a huge amount of the drug.
As the day wears on, metabolism starts to return to normal and the liver can begin to function properly. BUT.. with once or twice a day doses.. the body is HYPER any eight hour period without medication in the system.
Once a day doses...hyper the next 16 hours..then over dosed again.

This failure either on the doctor or patients part, is the reason PTU is second choice for small children. Physicians routinely prescribe adult size doses for the smallest children, due to their inexperience. Thus PTU now has a black box warning, and that was apparently over due.
There are records of liver transplants or death due to PTU at the rate of one per year....but keep in mind
*****In 2008, 340,000 individuals were prescribed methimazole and 101,000 individuals were prescribed PTU.*****

When an individual is over dosed on MMI, the longer half life ( 4 to 6 hours depending on patient status and source of info) lessens this hyper/ hypo each day, and small amounts of the drug are still detectable at the 24 hour period. Thus the liver can struggle, but it can keep up enough that once a patient understands WHY.. they can correct the problem.


Everything we swallow, breath, rub on our skin, is eventually processed through the liver.

Non-compliance :

The compliance with more frequent dosing schedule of PTU was only 53% compared to 83% with once daily MMI.11 These factors and the adverse effects profile of PTU have led to MMI/CBZ being the more popular first choice antithyroid drug

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2817786/?tool=pubmed

For patients that struggle to multi-dose, MMI is clearly the preferred choice. Much better than continuing dose errors with PTU. While MMI does not assist with the T3, an additional medication to treat that works fine.

Both are excellent medications when properly prescribed and taken. There's the trick.

Thanks for that Linda,

I forgot to add all liver problems reported have been with doses over 200 mg of PTU. That roughly translates to the 20 mg of MMI.

For me, I was fine on MMI, but PTU (even at a dose of 100mg) caused my liver enzymes to incease 2.5x's the normal limit. Most people are fine on MMI, unfortunately, it is not the preferred drug for pregnancy which is why I switched.

Okay Melanie, you got me there. I am not so good at short, fast replies. My last sentence is missing a word.
It should read:
I forgot to add all SERIOUS liver problems reported have been with doses over 200 mg of PTU. That roughly translates to the 20 mg of MMI.

Referring back to the first link I added , this is notable:
Mild to moderate elevations of the liver enzymes are common. They are often unexpectedly encountered on routine blood screening tests in otherwise healthy individuals. The AST and ALT levels in such cases are usually between twice the upper limits of normal and several hundred units/liter.

Rising liver enzymes are not unusual when hyper or when regulating ATDs. This applies to both ATDs. The upper limit for concern is more commonly considered five times the upper limit..then the person need to seriously consider stopping the drug, waiting a bit as things normalize, and switching to the other medication.

In order to correctly judge if it is the particular drug, or altered thyroid levels.. one needs to look at the current dose, history, and current labs. The most common reason liver enzymes rise, in the FT4 dropping too low within the reference range, plus the possibility that the doctor is dosing on TSH.. which will never work for a Graves' patient, no matter what treatment they choose.Most times simply lowering the dose to match the patients current needs, is the right choice.
Sometimes the patient is switched to the other ATD, and the dose is also lowered.

Choices.. we have choices. :)
You made the choice that fit best for you, while when my liver enzymes rose a couple times, I chose to lower my current dose and watch. For me..this was a better choice, due to my severe TED, coupled with my experienced endo's success healing TED with PTU as the preferred choice. I had already seen my fair share of less experienced endos.. so I decided to trust this endo. Turns out staying on the PTU and lowering the dose was the right choice for me.

We need to be aware, get labs done in a timely manner, run the right lab tests, and monitor. Keeping in mind serious liver complications are extremely rare, but we all need to be watched.That's only responsible medicine.

If the liver enzymes do rise..look at exactly how high they are and if your current dose is too high for your needs at that point. Also consider all other medications your liver is processing, if your taking your ATD all in one dose.. split it up through the day to ease the livers workload,and if you drink or smoke..cut it out.

No one choice is right for all of us and a blanket answer is never the whole story.

aaaww, wasn't trying to get ya Pam, you give fantastic advice! I just had a bad experience on PTU and was very disappointed that I had elevated liver enzymes, thus;shortening my time to be on ATD's and never achieving remission:( xoxo

Melanie, so you opted for TT, how did that turn out for you?

Melanie,

But you had a very good point. I did not phrase it correctly, and I appreciate the chance to remember to dot my i' and cross my t's. You keep me on my toes. I'm just so bad at explaining things in a few words. Some folks have the gift.. not me.

I'm so happy your still with us . Your success story post surgery is valuable. Treatment choice is so complex when we are first diagnosed, and some groups only seem to have the poor outcomes of all three treatments posted.

Hip, hip, hooray for our great group here. :)