CBD and Levothyroxine Interaction: How Does It Affect The Thyroid?

CBD’s apparent health benefits have led many people to try one or more of the many CBD products now on the market.

CBD (cannabidiol) is believed to help ease conditions like stress and depression, chronic pain caused by inflammatory or anti-immune disorders, neurodegenerative diseases like Parkinson’s and Alzheimer’s, insomnia, acne, and epilepsy, among others.

Another apparent benefit of cannabidiol involves thyroid health. Research suggests that CBD may help the body regulate its thyroid hormone levels, reducing the symptoms and complications caused by thyroid conditions like hypothyroidism, hyperthyroidism, and thyroid cancer.

The prescription medication levothyroxine (brand name: Synthroid) is a synthetic hormone that’s commonly prescribed to treat both hypothyroidism — the underproduction of thyroid hormones, which leads to slowing of the metabolism and potentially serious side effects — and thyroid cancer.

Here’s the issue that may confront some kidney patients, though: there might be problematic interactions between CBD and levothyroxine.

Cannabidiol is believed to trigger the release of additional thyroid hormones in some patients. But when those hormones are added to the synthetic hormone levothyroxine, there could wind up being too many thyroid hormones circulating in the bloodstream. That can cause either serious side effects or hyperthyroidism — a different but also troubling thyroid condition.

Additionally, CBD and the medication are each metabolised by the same liver enzymes, potentially overburdening those enzymes and leading to the release of too much CBD or levothyroxine into the system. The latter could cause the same problems mentioned above.

There’s an important qualification, however. No human cases of serious side effects or hyperthyroidism caused by CBD-levothyroxine interactions have been reported. These potential conflicts are only theoretical, although many medical authorities warn that they’re possible.

Some experts do suggest separating doses of levothyroxine and CBD by at least several hours to avoid potential interactions, while others say it’s safest to use just one or the other. The lack of conclusive data, however, means the decision is probably best made by a patient in consultation with their doctor or another healthcare professional.

For more details on what’s known and what’s not yet known, read on.

CBD and the Body

We’ll start with the basics.

What is CBD?

Plants in the Cannabis sativa family (hemp and cannabis) contain more than 100 natural compounds called cannabinoids. The two most important are psychoactive THC (tetrahydrocannabinol) and non-intoxicating CBD. Both appear to deliver impressive, although somewhat different, medical benefits.

Hemp has high levels of CBD and small amounts of THC, while cannabis contains lots of THC and very little CBD. That’s why marijuana is sourced from the cannabis plant, and the cannabidiol used to produce CBD products is extracted from hemp plants.

Cannabidiol isn’t absorbed well by the body unless it’s combined with a “carrier.” CBD oil and most other CBD products use a carrier oil like MCT oil or coconut oil, chosen because they are easily digested and preserve a good amount of the cannabidiol for use by the body.

CBD’s Path in the Body

CBD can be ingested in several ways. CBD oil is ideally dropped under the tongue because it works fastest and most effectively that way, but it can also be added to food or beverages. CBD capsules contain CBD oil, as do CBD edibles; the cannabinoid can also be vaped. (Topical CBD products usually only work externally, not inside the body.)

CBD oil administered under the tongue (sublingually) is quickly absorbed by the tissues located there and moved into the bloodstream. Vaped CBD is similarly absorbed quickly by lung tissues and sent on its way. The other administration methods first require digestion before CBD enters the bloodstream, delaying the cannabidiol’s effects and lowering its effectiveness significantly.

Cannabidiol delivers its effects by interacting with receptors in the body’s endocannabinoid system (ECS). The ECS governs an enormous number of crucial bodily functions, including thinking and memory, sleep, appetite, immunity, and inflammation. The receptors are located throughout the body.

CBD doesn’t proceed directly from the bloodstream to the ECS receptors, though. It must be metabolised by the liver before it can deliver its effects.

CBD and the Liver

The liver is responsible for breaking down the vast majority of drugs and other substances that are introduced into the body, including CBD. Liver enzymes convert cannabidiol into active metabolites that deliver the cannabinoid’s effects, and “waste” products to be excreted.

As with many other medications, the family of so-called CYP450 liver enzymes does most of the heavy lifting with one family member, CYP34A, doing the bulk of the work. Cannabidiol is turned into approximately 40 metabolites; the one primarily responsible for ECS receptor interaction is known as 7-COOH-CBD, but it’s easiest to simply refer to it as “CBD.”

Let’s pause this discussion for a moment to bring in the other important player.

What Is Levothyroxine?

Levothyroxine, commonly sold under the brand name Synthroid, is a synthetic hormone used to treat hypothyroidism (also known as underactive thyroid), enlarged thyroid glands, and a type of thyroid cancer. It’s the man-made form of the thyroid hormone thyroxine.

The drug is most often prescribed for hyperthyroidism, a condition characterized by insufficient production of hormones by the thyroid. Thyroid hormones are crucial for proper body function; a poor supply can slow everything from speech and movement to brain function and heartbeat while also producing fatigue, muscle weakness, weight gain, and depression.

Levothyroxine is an oral medication, which means it takes the same route through the body as most forms of CBD. After it’s swallowed, the pill is digested in the gastrointestinal system and the drug is then moved on to the liver for metabolisation. The enzyme CYP34A is also primarily responsible for that task, just as it is for cannabidiol.

The synthetic hormone is a first-line treatment for hypothyroidism and is usually taken for life. Dosing must be closely monitored, there are quite a few mild-to-moderate side effects and drug interactions to be aware of, and levothyroxine is contraindicated for some patients with heart disease, clotting issues, or adrenal gland issues. It’s quite effective for most users, however.

That brings us back to CBD.

Why Do Some Patients with Thyroid Issues Use CBD?

None of cannabidiol’s apparent benefits, with the exception of the treatment of several types of childhood epilepsy, have been acknowledged by the medical establishment or government regulators.

Even so, preliminary evidence for CBD’s apparent health and wellness benefits is strong. We’ve briefly mentioned some of the disorders, diseases, and conditions that may respond well to cannabidiol, but what matters for this discussion is its effect on thyroid health.

It’s been established that the endocannabinoid system plays a large part in overseeing thyroid function. And studies have shown that CBD’s interaction with the ECS appears to help regulate the production of thyroid hormones and keep them at optimal levels.

The evidence doesn’t suggest that cannabidiol stimulates the production of thyroid hormones in all users. However, since CBD’s apparent role is to maintain the proper hormonal balance, it would theoretically trigger the release of more thyroid hormones in patients with insufficient levels.

Again, CBD isn’t prescribed for hypothyroidism or other thyroid conditions — but initial research and anecdotal reports indicate that it could be a valuable weapon.

Taking Levothyroxine and CBD Together

There are no published reports on thyroid patients suffering serious problems when using both levothyroxine and CBD products. In fact, many patients do take both.

A large group of medical experts, though, suggest treading very carefully because of potential interactions between cannabidiol and levothyroxine.

There are two reasons for concern.

• If synthetic hormones (in the form of levothyroxine) have been introduced into the body, CBD may trigger the production of more thyroid hormones than the body needs at the time.
• Both the medication and cannabidiol are metabolised in the liver, and the same enzyme, CYP34A, is responsible for breaking down both of them at the same time.

That could theoretically lead to conflicts.

In the first situation, there could be unneeded synthetic thyroid hormones left to circulate in the system. In the worst case, that might result in an overdose and cause numerous side effects, some serious and occasionally fatal. The oversupply could also cause hyperthyroidism (too many thyroid hormones) — the opposite of hypothyroidism — which can also be serious.

In the second situation, metabolisation of the CBD or levothyroxine might not be completed. Either too much cannabidiol or too much levothyroxine could remain circulating in the bloodstream. An excess of CBD wouldn’t cause serious problems, but too much of the synthetic hormone could cause the same issues we’ve already mentioned.

It’s important to stress that no human cases of problematic CBD-levothyroxine interactions have been published in medical journals, so the likelihood of these issues arising appears remote, at least so far.

Some medical experts say the potential benefits of using both cannabidiol and levothyroxine to treat hypothyroidism outweigh what they say is a very small risk, while others recommend avoiding using them at the same time. A middle ground suggested by still others is to separate doses of levothyroxine and CBD by at least two hours to minimize the conflicts.

The best approach of all, though, would be for thyroid patients to discuss the pros and cons of CBD use with their doctor before combining cannabidiol and levothyroxine or other synthetic hormones.

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