In past articles and blog posts I have discussed some of the different conventional medical treatment options for hyperthyroid conditions, but I haven’t discussed something called block and replace therapy. One of the main reasons for this is because this is rarely recommended to those with hyperthyroidism and Graves’ Disease, although every now and then I’ll work with someone who was recommended to receive this treatment by their endocrinologist. As a result, I figured it was time to put together a brief post on this topic.
So what exactly is block and replace therapy? Well, many people with hyperthyroid conditions are told to take antithyroid medication, which includes Methimazole, Carbimazole, and PTU. These are given to “block” the production of thyroid hormone, and antithyroid medication accomplishes this by inhibiting an enzyme called thyroid peroxidase. What it specifically does is inhibit the metabolism of iodide and the iodination of tyrosine residues in the thyroid hormone precursor thyroglobulin by thyroid peroxidase (1).
One problem with antithyroid medication is that people who take it commonly become hypothyroid. So for example, it’s common for someone with elevated thyroid hormone levels to get a prescription for antithyroid medication, and when doing a follow-up thyroid panel their thyroid hormone levels will be low, while their TSH will be on the high side. When this is the case, the medical doctor will usually lower the dosage of antithyroid medication and hope that the next thyroid panel will show a lower TSH and higher thyroid hormone levels, but at the same time prevent the person from becoming hyperthyroid again.
The “Seesaw” Effect of Antithyroid Medication
Sometimes this can become a frustrating process for the patient, as I’ve worked with people who were told to take a higher dosage of antithyroid medication, and then when the thyroid panel revealed a hypothyroid state the dosage was greatly reduced, and in some cases the patient was told to stop taking the Methimazole, and the person became hyperthyroid again. So for example, a person with Graves’ Disease or toxic multinodular goiter might be told to take 40mg of Methimazole, and the next thyroid panel presents with hypothyroid numbers (elevated TSH and low thyroid hormone levels), and so the person’s dosage is reduced to 10mg, only to have the person become hyperthyroid again.
With block and replace therapy, the person isn’t only put on antithyroid medication to “block” the production of thyroid hormone, but they are also given thyroid hormone replacement (i.e. levothyroxine). So it’s almost like a balancing act, as the antithyroid medication will prevent the person from becoming hyperthyroid, but the person is also given some thyroid hormone to prevent them from becoming hypothyroid. Block and replace therapy is usually reserved for moderate to severe cases of hyperthyroidism, as with this treatment higher doses of antithyroid medication are usually taken by the patient.
Why Is Block and Replace Therapy Seldom Used?
Rarely does an endocrinologist in the United States recommend block and replace therapy, and it also isn’t commonly recommended by medical doctors in other countries. One reason for this is because the relapse rates are comparable to someone who is taking antithyroid medication alone, but another reason is because side effects seem to be more common with block and replace therapy (2). Another thing to keep in mind is that most endocrinologists are far more concerned about managing hyperthyroidism, which is why many will recommend radioactive iodine or thyroid surgery as the first line of treatment. In other words, many aren’t concerned if their hyperthyroid patients become hypothyroid by taking antithyroid medication.
This doesn’t mean that there aren’t times when block and replace therapy can be beneficial. For example, pregnant women with hyperthyroidism are usually told to take antithyroid medication. While many people are understandably concerned about the effects of these medications on the liver, another concern during pregnancy is that antithyroid medication can lead to hypothyroidism. And of course thyroid hormone is very important for the developing fetus. Block and replace therapy during pregnancy was discussed in a case study involving a 36-year old woman, as the authors explained how it is challenging to keep the free T4 in the upper range of normal with antithyroid medication alone, and that block and replace therapy can prevent fetal hypothyroidism from developing (3).
Graves’ orbitopathy might be another situation where block and replace therapy is indicated, as a study showed that using long-term block and replacement therapy until Graves’ orbitopathy becomes inactive might be a good option (4). One thing to keep in mind was that the patients in this study were treated with block and replace therapy for an average of 41 months, and many endocrinologists would refuse to have their patients take antithyroid medication for that long, even if the liver enzymes were fine during treatment.
The truth is that block and replace therapy might be beneficial in certain situations, but most endocrinologists are trained to prescribe antithyroid medication alone, which is why they commonly recommend this to their patients with hyperthyroidism and Graves’ Disease. In fact, some endocrinologists aren’t even familiar with block and replace therapy, and one reason for this is because only a small percentage of their patients have hyperthyroidism and Graves’ Disease. It is far more common for endocrinologists to deal with patients who have Hashimoto’s thyroiditis. As a result, those with a hyperthyroid condition can expect to be advised to take antithyroid medication by their endocrinologist, or to receive radioactive iodine or thyroid surgery.
In summary, block and replace therapy involves taking both antithyroid medication and thyroid hormone. So essentially the goal is to block the production of thyroid hormone, but at the same time have the patient take thyroid hormone replacement to prevent them from becoming hypothyroid. Block and replace therapy is rarely recommended by endocrinologists, and two reasons for this are because 1) the relapse rate is comparable to taking antithyroid medication alone, and 2) side effects are more common. However, pregnancy and Graves’ orbitopathy are two situations when this type of treatment might offer some benefits.
I successfully used block and replace therapy to get my mild-moderate Grave’s disease into remission. I started out on 10mg of methimazole for a few months then gradually added in the Synthroid, until I reached an optimal dosage of 75mcg/mg per day. Eventually, after reading your articles, I replaced the methimazole with bugleweed extract and continued the Synthroid treatment. It took a few years of daily treatment, but I have been off both medications for over two and half years with no signs of relapse yet.
Hi Christine,
Thank you for letting me know about this, as that’s pretty cool about using block and replace therapy with bugleweed instead of the methimazole! I’m glad you have been off of both medications for over 2 1/2 years.
Hello thanks for this. How much bugleweed should I use? I am on 1.25 tapazole and they want me on 100 mg synthroid starting today.
Hi Chris,
Although I can’t give specific dosing recommendations to non-patients, I will say that in order to normalize the antibodies you need to find and remove the autoimmune triggers. This can be very challenging to do, which is why I recommend working with a natural healthcare practitioner. But of course there are some things you can do on your own, such as eat a healthy diet, improve your stress handling skills, minimize your exposure to environmental toxins, etc.
I have been on block and replace with Strumazol and Thyrax for 20 years.
Once had RAI, without enough effect. When I was pregnant I got PTU and got vasculitis.
So after giving birth I went back to good old block&replace. I hope I can become 100 years old with it 🙂
Thank you for sharing your experience Marielle!
I have been Hyperthyroid on and off since 2011. I have always only ever been given carbimazole and my weight has gone from 60kg up to 78.7kg. I have asked my endocrinologist for block and replace but they will not do this for me. I am so frustrated and want to stop taking carbimazole of 40mg per day.
Hello, i’v been on block and replace therapy for 2 years, after very bad situation of very high blood pressure, 200/105 and a pulse 100. Stragle the whole month and “lived” almost in ER. By the way, before this first accident, I was diagnosed with Hashimotos, my TPO were not very high that time, only 32. I am taking 5 mg. Methimazole, 100mcg Synthroid and 30 mg Armour. I would love to stop all of them, but I am afraid, I can’t. I feel ok, but sometimes I still have hyper symptoms. Any helping answer will be greatly appreciated.
Rimma.
Hi Rimma,
I definitely wouldn’t advise you to stop taking all of your medications. The good news is that you’re on a low dose of the Methimazole, but of course you’re on a higher dosage of thyroid hormone replacement between taking the Synthroid and Armour. I would recommend working with a natural practitioner to help you address the cause of the problem, which should eventually allow you to wean off of the Methimazole, and hopefully the damage to your thyroid gland isn’t too extensive where you can also slowly wean off of the thyroid hormones. But either way you want to address the cause of the problem, although you of course want to do this cautiously.
Yesterday my Endo prescribes block and replace after 2 years being on low dose tapazole. Today I am on 1.25 mg tapazole per day. I am becoming hypo. Tsh is 1.6 ( perfect) and t4 13 (just below midpoint) and t3 is below recommended at 2.9 I still have TSI antibodies at 3.8 pui/l. He is recommending block and replace for 6 months to eliminate my graves antibodies. I really don’t want to be on these meds anymore. How can I eliminate antibodies and get
My thyroid labs to mid point using natural methods. I’m so close as antibodies have come down significantly but still there
Hello could anyone help me I’m desperate. I’ve had graves disease for 7 years now and been on different Medication nothing has worked. Endo has now put me on 200mg propylthicouril 3 times daily and 125mg thyroxine . I’ve been referred for surgery. Anyway since ive been on these tablets I’m getting alot of headaches, sore dry itchy eyes. But most importantly I’m loosing alot of hair and I mean alot and it’s getting me so down. Crying as I write. My hair is only thing I like about myself. Plz help
Hello
I’ve been on block and replace for about 3 years. And my endo going to take me off meds soon. Being on block and replace feels like the optimal solution for my graves. Would it be possible to stay on meds for as long as I feel ok? Meaning for maybe another 3 years at least and see how it goes? Thank you.
Elvira, I know some people do fine on low dose methimazole for a long period of time. And so if you are taking only 5 to 10 mg of methimazole per day along with the thyroid hormone replacement, and assuming your liver enzymes look fine, then you probably would be okay continuing with this. That being said, while doing this I would still try to address the underlying cause of your condition so that hopefully you don’t need to rely on the medication on a long-term basis.
Hello dr. Osansky!
I have been put on B & R therapy about 2.5 months ago (before that I was taking 10mg of methimazole daily, for about 2 months, but since my thyroid started to work too little and my antibodies dropped, they added 25mcg Euthyrox). Latest lab results show elevated TSH (4.08, upper range is also near that number), normal T4 (18, upper range is 22) and also low T3 (3.79, lower range is also somewhere here, around 3 point something). While I generally feel quite okay, except for adrenaline/anxiety rush in the morning every once in a while (maybe every 2 weeks once, when triggered by stress/my mind), I noticed hair falling out for about a month now. My hair is at the same time getting very greasy, so I have to wash it every 2 days (before that I could wash my hair every 3 or 4 days). Whenever I wash it, there’s about 3-4 times more hair in the sink and it makes me want to cry. I said to my thyroid doctor, please put me on 5mg of methimazole instead and ditch 10mg dose and combination with Euthyrox, specially if my antibodies will still be absent this time. I’m still waiting for results. She was not keen on this idea, always saying their goal is to keep me on medication for at least a year (year and a half), because best research specialists are saying remissions are longer that way.
Please, do you think T3 at lower range and elevated TSH could be causing hair loss? My doctor just said: ”Well, I don’t know. People usualy mention more hair loss in this stage of the disease/in this time (half of year on meds).” As if it was normal. She always somehow convinces me to trust her choices even though I am often very agressive about it, just to think about it at home. I always feel I have to fight against doctors.
I read your article on hair loss. Let me add that I have been taking 100 – 200 mg of selenium for a few months now (and even assumed I was getting too much of it and this is the reason for hair loss). I do follow gluten-free, dairy-free diet, rarely eat nuts and eggs, don’t drink any coffee, alcohol, visit acupuncture sessions, do yin-yoga at home and take probiotics with prebiotics, omega 3 capsules and vitamin C (I have been taking multivitamins as well, but my doctor wanted me to ditch those – concerns went about iron and calcium as disruptors of the meds absorbtion).
I would appreciate it lots if you could let me know if low T3 (even if having excellent T4) and TSH in higher range are potentially the cause of this and if this is caused by B & R therapy? (meaning my body does not convert Euthyrox well). Thank you!