# How I Overcame Low Thyroid Function with Ray Peat's Help – and How to Test Your Own

By Dr. Benedicte Lerche · Thyroid Health · Published 2026-10-05

> Dr. Benedicte Lerche on recovering from low thyroid function, how to test your thyroid with pulse and temperature, and what to eat.

Summary

-   At 19, low thyroid function left me too tired to start university. Years of correspondence with Dr. Ray Peat helped me recover.
-   Blood tests are useful, but resting pulse, temperature after breakfast and your symptoms give a fuller picture.
-   High stress hormones can hide low thyroid function – and can even be mistaken for an overactive thyroid.
-   Estrogen, unsaturated oils, too much iodine, crash diets and long gaps between meals all slow the thyroid.
-   The full conversation is on the Kick It Naturally podcast, linked below.

## How it started

I have possibly had slightly low thyroid function my whole life. But at 19, something tipped me over. I caught a very serious infection, and even after the infection was over, my body simply couldn't get out of that state.

The doctors couldn't find anything wrong with me. Yet I was tired all the time, I had headaches, and I struggled with low blood sugar. I wasn't able to start my university studies – a hard place to be at 19.

I was lucky to come into contact with a Danish doctor who knew a little about hypothyroidism, and I was diagnosed with low thyroid function. But I soon found that Danish doctors knew very little about how to handle the treatment: what to expect from the medication, how to adjust it, and which diet was right for someone with my symptoms.

## Finding Ray Peat

So I turned to the internet. This was around 2000, in the early days of the internet, and I spent hours and hours searching. In one person's references, I found the name Ray Peat – and a phone number.

I called him, and he picked up. I asked him a couple of questions, and he gave me his email address and his website. Luckily I wrote them down correctly, because that was the start of a long correspondence.

Ray Peat helped me understand why my body had ended up in the state it was in, and how to use the thyroid medication I had been given correctly. Getting well is a process. It is not something you do in a week, and there are many adjustments along the way. He helped me through that process, and he was extremely helpful.

That is what I try to do today through BiochemNordic. I take Ray Peat's books, articles, newsletters and interviews and turn his ideas into a program people can use in their everyday lives. His writing is full of biochemistry – even I sometimes have to look things up to follow it – so my job is to make it practical.

## Why thyroid function matters so much

The thyroid is the main controller of energy in your cells. When cells don't have enough energy, they can't carry out their essential tasks. That is why low thyroid function affects everything in the body, and why it causes so many different symptoms.

## How to know if your thyroid is working well

### Blood tests: useful, but not enough

The most helpful blood tests are total T4, total T3 and TSH. The thyroid gland, in the front of your throat, releases two hormones, T4 and T3. TSH, thyroid-stimulating hormone, comes from the pituitary gland. It is the brain's signal telling the thyroid to work harder, so a high TSH suggests your thyroid is underactive.

The problem is the "normal" range on the lab report. It is very broad, for historical reasons. Many people sit in the lower end for T4 and T3, are told they are normal, and still have all the symptoms. The test isn't useless – the range is simply so wide that you can easily be hypothyroid with a so-called normal result.

### Pulse and temperature

According to Ray Peat, an easy way to test your thyroid function is to measure your resting pulse and your oral temperature:

-   Pulse: someone with good thyroid function has a resting pulse of around 85 beats per minute. 80 is also fine – around 80–85.
-   Temperature: around 98.6°F (37°C) during the day, measured under the tongue. An ordinary digital thermometer is fine; it doesn't need to be expensive.

### Why you should measure before and after breakfast

Some people with low thyroid function wake up with a high pulse or a high temperature. That is because their stress hormones are high and are compensating for the low thyroid function. When they eat breakfast, their blood sugar rises, the stress hormones fall, and the numbers come down. The numbers you measure after breakfast are the ones that reflect your thyroid function.

Measuring both before and after breakfast also tells you something about your stress hormones. If you wake up with a pulse of around 100 and it is down to 70 twenty minutes after breakfast, that strongly suggests very high adrenaline. And if your pulse and temperature fall after eating to well below 80 beats per minute and 98.6°F, something is going on with your stress hormones too.

### What about athletes?

A highly trained athlete will have a lower pulse and still be healthy. The problem is assuming that a low pulse must be a sign of fitness. If you are not training a lot and your pulse is 65, that is not a good sign. It means everything in your body is running at a slower rate – your metabolism is simply too low.

### Don't forget your symptoms

Your symptoms complete the picture. Common ones are fatigue, frequent infections, allergies, poor sleep, weight gain – or weight loss – thinning skin and hair, digestive problems, cold hands and feet, and blood sugar swings. We all have our weak spots, so the symptoms differ from person to person.

## When low thyroid looks like an overactive thyroid

Very high adrenaline can make you hyperactive, restless and jittery. You can't sleep, you can't sit still. Many doctors see this as a sign of an overactive thyroid and give medication that destroys or inhibits the thyroid gland.

In my experience, people with low thyroid function being diagnosed as overactive is a bigger problem than people who really are hyperthyroid. A true overactive thyroid exists, but it is not common compared to the opposite.

There is a simple clue. If your high pulse is caused by adrenaline, it drops when you eat. If it is caused by a genuinely high metabolism, eating doesn't make it drop.

## Estrogen and the thyroid

Estrogen inhibits thyroid function in several ways. One is by blocking the release of thyroid hormone from the gland, which is why women more often develop a goiter: the gland grows because the hormone can't get out.

This also explains why some women feel their thyroid works better during pregnancy. Progesterone, the body's natural anti-estrogen hormone, is very high during pregnancy. After delivery, progesterone drops sharply, estrogen rises again, and thyroid function slows down.

Much of the estrogen problem can be corrected with diet:

-   Avoid birth control pills containing estrogen.
-   Eat enough protein. Without it, your liver can't clear estrogen properly.
-   Be careful with soy, beans and lentils, which are estrogenic.
-   Avoid grapefruit, which inhibits a liver enzyme you need to clear estrogen.
-   Be aware that many over-the-counter supplements are estrogenic, even when they are promoted as healthy.

One important caution: if you have a large goiter, starting progesterone right away is not a good idea. It can make the gland release all its stored hormone at once and push you into an overactive state that is hard to control.

## Thyroid medication: what to know

I don't prescribe anything. I educate people about what to do and what not to do. And the most important point about thyroid medication is this: don't use a pure T4 medication.

T4 has to be converted into the active T3. Healthy young men usually manage that conversion, so T4 alone works for them. But many women have trouble with pure T4 medication such as Synthroid – which is still the standard prescription in Denmark, most of the US and Europe.

Natural desiccated thyroid, made from pig or cow thyroid glands, contains both T4 and T3 and is usually okay. It was excellent in the 1960s and 70s, but production has since become less reliable. Ray Peat therefore started recommending synthetic T4 and T3 instead, usually in a 4:1 ratio – four times as much T4 as T3, close to what our own gland releases. Some people do better on 3:1 or 2:1. It is very individual.

Is it safe to take thyroid hormone? While you take it, your own gland rests. But it doesn't lose the ability to work. If you later reduce the dose slowly and stop, your own thyroid gradually resumes its production.

## Iodine: more is not better

It is a common idea that people with thyroid problems should take extra iodine. But too much iodine can suppress the thyroid, and I know many people who became hypothyroid from taking too much. According to Ray Peat, excess iodine can create a kind of inflammation in the gland.

The best way to get the right amount is to eat shellfish – shrimp, lobster or crab – about once a week. That gives you iodine along with other trace minerals the thyroid needs. I also use salt without added iodine.

## Why crash diets backfire

When you cut calories hard, your body treats it as an emergency: less food is coming in, so it lowers your metabolism to save what it has. When you go back to eating normally, the weight comes back. That is why Ray Peat recommends losing weight extremely slowly, if you need to lose it at all.

## What to eat to support your thyroid

1.  Swap unsaturated oils for saturated fats. This is the most important change. Unsaturated oils inhibit thyroid function in several ways, so replace liquid oils with coconut oil and butter. That also means cutting back on nuts, grains and seeds, which are high in unsaturated fats.
    
    Be patient: if you have eaten unsaturated fats for years, they are stored in your fat cells, and it can take up to four years to replace them. Every time you get hungry, stress hormones release stored fat into the blood, so the old fats keep slowing your thyroid. Eating saturated fat helps balance this out, because it is the ratio between the two types that matters.
    
2.  Eat sugar – the right kind. The liver needs glucose to convert T4 into active T3. When your blood sugar drops, your metabolism drops immediately. Fruit, orange juice, watermelon and tropical fruits contain both fructose and glucose. Honey and white sugar have the same 50/50 composition; honey is slightly better because it also contains minerals. Fructose actually helps cells take up and use glucose.
3.  Go easy on starch. Bread, pasta and rice are pure glucose. They cause a sharp blood sugar rise, an insulin spike, a dip in blood sugar afterwards – so you get hungry faster – and they promote fat production.
4.  Eat enough protein, so your liver can do its job, including clearing estrogen.
5.  Avoid foods that suppress the thyroid:
    -   cooked carrots and carrot juice (raw carrots are fine, because the carotene stays bound to the fibre)
    -   raw cabbage-family vegetables, which interfere with thyroid hormone production
    -   sauerkraut, because of its lactic acid
    -   soy, beans, lentils and grapefruit

## What about coffee?

Coffee is anti-inflammatory and protective – it has been linked to protection against Alzheimer's. But black coffee on an empty stomach can disturb your blood sugar and cause a stress-like reaction. Drink it with milk and sugar, or with food, and you get the benefits without the stress.

## Listen to the full interview

This interview was first broadcast on the Kick It Naturally podcast with Kyra McEnroe, T.C. Hale and Will Schmidt. [Watch it on YouTube](https://www.youtube.com/watch?v=dry9tOGZSjQ). [See all my interviews](/media).

## Learn more

For my full story, see my book How I Overcame Hypothyroidism. For my diet and thyroid medication principles, see my books How to Boost Metabolism with Food and How to Use Thyroid Medication, and my Metabolic Food Mastery™ and Thyroid Optimization™ courses.

## Frequently asked questions

### What is a healthy resting pulse for thyroid function?

Around 80–85 beats per minute, measured after breakfast, unless you are a highly trained athlete.

### Can you have low thyroid function with normal blood tests?

Yes. The normal ranges are broad, so pulse, temperature and symptoms give a fuller picture.

### Can low thyroid be mistaken for an overactive thyroid?

Yes. High adrenaline can cause restlessness and a fast pulse. If the pulse drops after eating, adrenaline is the likely cause.

### Should I take iodine for my thyroid?

Usually not. Too much iodine can suppress the thyroid. Shellfish once a week is a better source.

### Is coffee good for the thyroid?

Coffee is anti-inflammatory, but drink it with milk and sugar or with food, not black on an empty stomach.

**Tags:** hypothyroidism, low thyroid function, thyroid testing, Ray Peat, pulse and temperature, thyroid diet, thyroid medication

Source: https://biochemnordic.com/blog/how-i-overcame-low-thyroid-function-with-ray-peats-help