Thyroid Specialist, Benedicte Lerche MSc PhD

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Thyroid Meds guide

This guide explains our recommendations on thyroid mediactions. We do not prescribe or sell any medication, thus this guide is meant as a guide for you who are on prescription thyroid medication from your doctor, and want to know more about good kinds of thyroid replacement therapy and how to use it correctly. 

Our recommendations on thyroid medications are based on the research of Dr. Ray Peat. 

The important thing when using a thyroid replacement therapy is to use a product with both of the thyroid hormones meaning both T4 and T3.

In this guide, we present important information on both natural desiccated thyroid medications as well as synthetic thyroid hormone medications. 

If you do not have a prescription for thyroid hormone our Natural Desiccated Thyroid Guide presents good brands of over-the-counter natural desiccated thyroid supplements. 

It is always important to use our thyroid-supportive diet recommendations together with any thyroid medication. Our Hypothyroid Treatment Program goes into detail about our thyroid promotion diet recommendation which is based on the famous Ray Peat diet.

Armour-thyroid function

What is Natural desiccated thyroid (NDT)?

Natural desiccated thyroid (NDT) also called thyroid extract is a dried powdered thyroid gland from an animal, usually from a pig (porcine thyroid) but it can also be from a cow (bovine thyroid). If manufactured correctly, these thyroid extracts provide a similar ratio of T4 and T3 to that secreted by the human thyroid gland. These extracts were the first type of medication for treating hypothyroidism, now the thyroid hormones have been synthesized, and synthetic hormone therapy is also available. 

Often it will be stated on the bottle of a natural desiccated thyroid medication how many micrograms (mcg) of T4 and T3 it contains, however, it is important to understand that these natural thyroid extracts do not contain any free hormones, but thyroid tissue, where the thyroid hormones are bound to proteins called thyroglobulin, just as in the human thyroid gland. When the thyroid extract is degraded in the human digestive system, the T4 and T3 are released into the bloodstream. Since pig’s and cow’s thyroid glands contain T4 and T3 in ratios very close to the human thyroid gland, one cannot go very far wrong with good natural thyroid extracts.

Many of the NDT products on the market are prescription drugs, including Armour thyroid, Erfa thyroid, and NatureThroid, whereas others are non-prescription supplements.

The story of Amour thyroid

According to Ray Peat, the original natural desiccated thyroid product called Armour thyroid made by Armour & Company was a very good product. Armour & Company invested a great amount of research in making their thyroid extract, and they tested the strength of every batch on mice to make sure that it had a consistent potency!

But Armour & Company sold the Armour thyroid brand, and it went through a number of sales over the years, resulting in different companies making changes to the original formula, including changing the binders in the tablets, creating problems with the tablets not releasing the thyroid hormones probably upon digestion.

According to Dr. Ray Peat, the current manufacturers of Armour thyroid and other natural desiccated thyroid products, do not have access to the research made by Armour & Company. 

When the manufacturers change their additives and binders the potency of the thyroid tablets change, and they do not have the capacity to test the potency of their products on mice, as Armour & Company did.

Thus the prescription natural desiccated thyroid (NDTs) on the market today are simply not as reliable as the original Armour thyroid, which is why Dr. Ray Peat often recommends synthetic thyroid therapy.

However, Dr. Ray Peat also states that since the formulas and production methods of the natural desiccated thyroid products are often changed, trying different brands of natural desiccated thyroid, until you find a product that works, is an option if you prefer a natural glandular over synthetic medication.

At the moment Dr. Ray Peat has the most confidence in Armour thyroid compared to the other natural desiccated thyroid medications. 

Usually, naturopathic doctors are willing to prescribe natural desiccated thyroid such as Armour thyroid. 

If you do not have a prescription for thyroid hormone our Thyroid supplement Guide presents non-prescription natural desiccated thyroid products with high thyroid activity.


The problem with pure T4 medication?

When doctors treat hypothyroidism they usually prescribe a synthetic T4 medication. In order to understand why a pure T4 medication is problematic, it is important to remember that the active thyroid hormone is T3 and that T4 is the storage hormone, which is converted to T3 in the tissues, mainly in the liver.

When the effect of pure T4 medication was tested, it was done on healthy young male medical students, and in them, it worked very well, as healthy males have no problem converting T4 to the active T3 hormone.

However, women and seriously hypothyroid people often have trouble on a T4 medication, because they have a less effective liver function and thus less effective conversion of T4 to T3.

The brain concentrates T3 and is very sensitive to too much T4. When T4 is not converted efficiently to T3, it accumulates and the T4 in itself will have anti-thyroid effects, leading to the many symptoms of low thyroid function. Thus as the dose of T4 is increased the symptoms often get worse.

In order to defend itself from too much T4, the body starts converting T4 to reverse T3 (rT3), which blocks the effect of T3.

The accumulation of T4 will down-regulate the secretion of the TSH from the pituitary gland, and thus eventually the T3 that was coming out of the thyroid gland will also decrease leading to even lower T3 and worsening of low thyroid symptoms. In our blog post on reverse T3, you can learn more about this subject. 

In our Hypothyroid Treatment Program, the thyroid system is described in detail, including the function of the thyroid hormones ( T4, and T3) as well as the thyroid-stimulating hormone (TSH).

Synthetic thyroid therapy?

A synthetic thyroid hormone therapy should always be a combination treatment with T4 and T3, although we sometimes recommend a pure T3 treatment, in the case of a severe conversion deficiency, where you are unable to convert T4 to T3.

You can use a T4 medication such as Synthroid and combine it with a medication containing pure T3, there are also products that contain both T4 and T3 in one pill (combination drugs).

Many of the same problems that exist for natural thyroid products also apply to synthetic products. It is not straightforward to compound pills with synthetic thyroid hormones, so they release the hormones well upon digestion, and some of the synthetic thyroid medications on the market, do not function well. So if you are on synthetic thyroid medication and you feel that it isn’t working changing to another brand is worth considering. 

As for natural thyroid extracts, there are many pharmaceutical manufacturers of synthetic thyroid hormones, here are some combination drugs as well as pure T3 products that are recommended by Dr. Ray Peat:

T4 & T3 combination drugs:

Cynoplus: Contains T4 and T3 in a ratio of 4:1 

Proloid-S: Contains T4 and T3 in a ratio of 4:1

Thyrolar: Contains T4 and T3 in a ratio of 4:1

Novothyral (or Novotiral): Contains T4 and T3 in a ratio of 5:1

T3 drugs:

Cytomel:  Contains pure T3

Cynomel: Contains pure T3

Thybon: Contains pure T3

Cynoplus-Ray Peat
Strength Conversion Between Natural  And Synthetic Thyroid Medication​

Strength Conversion Between Natural And Synthetic Thyroid Medication​

The strength of natural desiccated thyroid is given in grains, with one grain corresponding to 60 mg of thyroid extract. The strength of synthetic thyroid drugs is given in mcg. One grain natural thyroid corresponds approximately to 50 mcg T4 + 12,5 mcg T3, or 25 mcg pure T3.

Thyroid drug conversion

The table above shows a thyroid drug replacement chart, which outlines the approximate equivalent strength conversion between natural desiccated thyroid and synthetic drugs.

Thyrolar tablets have been made in strengths that follow the grain system:

  • Thyrolar -½ (25 mcg T4 + 6,25 mcg T3) corresponding to ½ a grain
  • Thyrolar -1 (50 mcg T4 + 12,5 mcg T3) corresponding to 1 grain
  • Thyrolar -2 (100 mcg T4 + 25 mcg T3) corresponding to 2 grain
  • Thyrolar -3 (150 mcg T4 + 37,5 mcg T3) corresponding to 3 grain

Cynoplus, Proloid S, and Novothyral do not exactly follow the grain system:

  • Cynoplus (120 mcg T4 + 30 mcg T3) corresponding to a strength of 2 – 3 grain
  • Proloid s (30 mcg T4 + 7,5 mcg T3) corresponding to a little over ½ grain
  • Proloid s (60 mcg T4 +15 mcg T3) corresponding to a little over 1 grain
  • Novothyral (100 mcg T4 + 20 mcg T3) corresponding to a little under 2 grains
What is a normal thyroid dosage?

What is a normal thyroid dosage?

The traditional adult dose of Armour thyroid was about two grains (120mg) per day. The properly working human thyroid gland produces the equivalent of about four grains of natural desiccated thyroid per day, so with two grains or the synthetic equivalent of (100 mcg T4 and 25 mcg T3), there isn't a risk of overdosing. 

  • The full adult dosage of thyroid medication is about two grains, but it is very individual how a person responds to the thyroid replacement therapy though. Because the need for thyroid will depend on the diet, other hormones, and weather (in the summer the thyroid requirement is often less than in the winter).

  • People often do well enough on the ratio of T4 to T3, which is present in the combination drugs. But, as the human thyroid gland releases T4 and T3 in the ratio of about 3:1, many people feel better if they take that ratio or even a 2:1 ratio of T4 to T3. In these cases, extra T3 (Cytomel or Cytomel or Thybon) can be added to the combination drugs to obtain the desired ratio between T4 and T3. Here are some examples: 

  • Using Cynoplus (120 mcg T4 + 30 mcg T3) and Cytomel (25 mcg T3) tablets a daily dose corresponding to about 2 grains would be: Cynoplus 3/4 of a tablet + Cynomel 1/4 tablet = 90 mcg T4 + 28,8 mcg T3,  3:1 ratio (T4:T3).

  • Cynoplus 1/2 of a tablet + Cynomel 1/2 of a tablet = 60 mcg T4 +27,5 mcg T3, 2:1 ratio (T4:T3)

  • Using Novothyral (100 mcg T4 + 20 mcg T3) and Cynomel (25 mcg T3) tablets a daily dose corresponding to about 2 grains would be:

  • 3/4 tablet of Novothyral + 1/2 tablet of Cynomel = 75 mcg T4 + 27,5 mcg T3  3:1 ratio T4:T3

  • Using Novothyral (100 mcg T4 + 20 mcg T3) and Thybon  (20 mcg T3) tablets – a daily dose corresponding to about 2 grains would be:

  • 1 tablet of Novothyral + 1/4 tablet of Thybon = 100 mcg T4 + 25 mcg T3  4:1 ratio T4:T3

  • 3/4 tablet Novothyral + 3/4 Tablet Thybon   = 75 mcg T4 + 30 mcg T3  2,5:1 ratio T4:T3

  • Dosis corresponding to  2 ½ grains:

  • 1 tablet of Novothyral + 1 tablet of Thybon = 100 mcg T4  + 40 mcg T3   2,5:1 ratio T4:T3

How to use a thyroid medication?

How to use a thyroid medication?

When you use a thyroid product containing T3, you will need to divide your daily dosage, and always have your thyroid product with food.

  • T4 has a half-life of two weeks and thus accumulates in the body over time. On a given dose a steady concentration will be reached after about two weeks. T3, on the other hand, has a very short half-life and has an immediate effect on cells. Importantly the effect of  T3 will disappear within a couple of hours, thus T3 does not accumulate. 

  • Under normal circumstances, the body produces about four mcg T3 per hour (about 100 mcg per day). It is very important not to take too much T3 at any time, since that would not be physiological correct, and the body would have to protect itself from too much T3, by inactivating it in the liver.

  • When using a synthetic thyroid hormone it is important to never have more than 5 mcg of T3 in any dosage and always have it with a meal. If T3 is used outside meals, the dose should never be more than 4 mcg per hour, but it could be 1-4 mcg every other hour.

  • Natural desiccated thyroid products also contain T3, although the T3 is not free, but released upon digestion of the thyroid extract. In order to maximize your benefits from the T3 in the natural thyroid product, you need to divide your daily dosage and take your natural thyroid product 2-3 times per day, and always with food.

Finding your optimal dosage

Finding your optimal dosage

When beginning a thyroid supplement it is very important to start on a very low dose and slowly work up to the higher maintenance dose, which is usually what corresponds to about 2 grains.

  • When starting up on thyroid replacement therapy the important thing is to go slow and gradually work yourself up to the ending dosage. If you jump right in and use what you think is your ending dosage right away, you will probably experience problems.
  • The usual starting dose of the original Armour thyroid was half a grain per day, corresponding to about a quarter of a Cynoplus tablet (25 mcg T4 + 6,5 mcg T3). Some people need to start on an even lower dosage, something like 1/8 of a Cynoplus. The more hypothyroid you are the more likely you are to experience negative symptoms if you start up on thyroid medication with too high a dosage.
  • With synthetic drugs, it is possible to vary the ratio between T4 and T3 to best suit the body’s needs. Some people need more T3, especially in the beginning stages of the treatment. When the liver is not efficiently converting T4 to T3, it can be necessary to take T3 four or more times during the day, until normal puls and temperature have been established and stabilized.
  • On a certain thyroid dosage T4 accumulates in the tissues, and its action will increase until equilibrium is reached, which usually takes about two weeks.
  • When starting up on thyroid therapy. It is essential to keep track of the pulse rate and body temperature for instance by using a chart like the one shown below. The temperature should be close to 98.6 F ( 37C), and the pulse around 85 beats/min, when your thyroid function is optimal.
  • See our Home Thyroid Test for important information on using pulse and temperature to measure your thyroid function.
  • If the numbers haven’t risen after a week, the daily thyroid dose is too low and can be increased until the numbers start moving towards the goal at 85 beats per minute and 96,8 F (37 C).
  • If the lines are rising so fast that they will reach the goal temperature and pulse rate in just a few days, the dose is too high (at least for the present) and should be reduced.
  • When the body has accumulated a steady level of T4 (which takes about two weeks) and begin to function at a higher metabolic rate, the stress hormones often begin to come down, which can lead to a pulse and temperature drop.
  • Hypothyroid people very often compensate for the low thyroid function with high levels of adrenalin and cortisol. As the stress hormones normalize the early effects of thyroid supplementation may seem to decrease, with pulse and temperature declining. The daily dose of thyroid then needs to be increased at this point. This may happen several times, as the thyroid function starts to take over and the stress hormones decrease.
  • In summary, you should start on a very low dosage of thyroid hormone, and always have your thyroid medication with food. You should divide your thyroid dosage so you don’t get more than 5 mcg of synthetic T3 with any dose. With the natural dessicated thyroid it is important to devide your daily doses as much as possible. 
  • You should stay on the same daily dosage for at least two weeks before increasing it. As the stress hormone normalizes you might see a drop in temperature and pulse rate at which point you should increase your medication. It can take several months to reach your ending dosage of thyroid hormone.
  • You should keep track of your pulse and temperature in order to evaluate the effect of your thyroid medication. Looking for symptoms of hypothyroidism such as cold hands and feet is also important, see more in our Home Thyroid Test. 
test your thyroid at home
Further Thyroid Support

Further Thyroid Support

Many aspects of using thyroid replacement therapy are very complicated, here are some aspects you should be aware of if you wish to use thyroid replacement therapy.

  • If you do not have a prescription for thyroid hormone and you need thyroid replacement therapy, we recommend using a non-prescription thyroid supplement. However, it is important to mention that many over-the-counter thyroid supplements on the market contain no active thyroid hormone, and thus don’t work! In our Thyroid Supplement Guide, we present non-prescription thyroid supplements that works!

  • Thyroid therapy leads to an increased need for nutrients and can reveal a nutritional deficiency. Thyroid therapy should thus always be combined with nutritional optimization and possibly the use of certain nutritional supplements. 

  • When people have very low cholesterol, it is important to increase the cholesterol before taking thyroid, since the steroid-forming tissues (which produce pregnenolone and progesterone from cholesterol) won’t be able to respond properly to the increased thyroid function without adequate cholesterol.Low cholesterol people can often get very unpleasant symptoms if they don’t increase their cholesterol at the same time as using a thyroid replacement therapy. 

  • Sometimes it is often helpful to supplement with progesterone and or pregnenolone in order to support the body’s natural anti-aging and anti-stress systems while increasing metabolism. In our hormonal support guide, you can learn more about using pregnenolone and progesterone supplements to avoid stress and unpleasant symptoms, while increasing thyroid function, in our hormonal support guide here.

  • Increasing thyroid function too quickly can result in unpleasant side effects for some people, especially if they have been hypothyroid for a long time. Many aspects of using thyroid therapy can be very difficult, and fine-tuning the treatment to your body’s needs is often complicated. It is thus strongly recommended that you use our consultation service.