Thyroid disorders are one of many diseases that, like fibromyalgia or endometriosis, are common but under-diagnosed, perhaps because they predominantly affect women. In the United States alone, about 20 million people suffer from thyroid disorders, of whom about 60% are not even aware of it. In France, the proportions are similar, with an estimated 10-15% of the population suffering from thyroid problems.
Currently, the majority of thyroid patients are prescribed hormone substitutes. These simply replace the thyroid in the tasks it cannot perform. But they do not act directly on the thyroid and have many side effects which, in some cases, can be very inconvenient. More and more patients are therefore choosing other types of medication. Hence the question of whether cannabis may play a role in the fight against thyroid disorders.
What is the thyroid and what does it do?
The thyroid is a gland of the endocrine system that lies under the larynx. Through the production of two hormones – T3 (triiodothyronine) and T4 (tetraiodothyronine) – it controls metabolism by determining how the body’s cells use their energy, hence its importance in regulating weight, managing mood and controlling physical and mental energy levels.
But sometimes the thyroid can malfunction. The two most common forms of thyroid dysfunctions are hyperthyroidism – which is an overproduction of thyroid hormones – and hypothyroidism – which is an underproduction of these hormones.
Hyperthyroidism is thought to affect about one in a hundred women and can be caused by excessive consumption of iodine or tetraiodothyronine, by inflammation, by tumours (of the testicles, ovaries, pituitary or thyroid itself) or by certain diseases (Graves’ disease, multinodular goitre or toxic nodular goitre). Symptoms of hyperthyroidism include fatigue, weight gain, constipation, hair loss, increased cholesterol levels and/or increased coldness.
Hypothyroidism is usually caused by Hashimoto’s disease or damage to the thyroid from radiotherapy. Most of the time, hypothyroidism is benign, with symptoms such as tremors, heat intolerance and sweating, irritability and/or increased appetite.
Can cannabis help with thyroid problems?
Scientists are concerned about the possible influence of cannabis on the thyroid because several studies have shown that there is a close link between the thyroid and the endocannabinoid system.
In the 1970s and 1980s, researchers noted that cannabis reduced thyroid hormone levels in rats. More recently, a study published in the European Journal of Endocrinology showed that CB1 receptors modulated the release of T3 and T4 thyroid hormones in the same animals. The authors therefore suggested that cannabinoids could play a role in regulating thyroid activity in the rodents.
But our understanding of the relationship between cannabinoids, the endocannabinoid system and the thyroid goes beyond rodents. A 2009 study showed that, in humans, CB1 receptors of the endocannabinoid system interact directly with neurons responsible for thyroid control. Another study, published in 2015, confirmed these findings by showing that cannabinoid receptors could act on thyroid damage.
In view of this link between the endocannabinoid system and the thyroid, it seems legitimate to question a possible relationship between cannabis use and thyroid disorders. Only a few studies have been devoted to this question. Fortunately, one of them is quite remarkable in its scope.
For several decades, the National Center for Health Statistics in the United States has been producing annual reports to assess the health of Americans. In 2017, a team of researchers studied the reports produced between 2007 and 2012 with the aim of assessing the effects of cannabis on the thyroid function of users. In total, data from 5,280 people aged 18 to 69 were analysed. It was found that those who had used cannabis in the month before the analyses had lower thyrotropin levels than non-users or those whose last cannabis use was more than one month ago. Thyrotropin (or TSH) is a hormone secreted by the pituitary gland that regulates the release of thyroid hormones from the thyroid gland. In other words, the higher the thyrotropin level, the more active the thyroid. It could therefore be deduced from this study that cannabis use leads to transient hypothyroidism.
This hypothesis is corroborated by another study carried out in 2008 in which the authors noted an under-excitation of the thyroid system in people who use cannabis for long periods.
But things are not so simple, since another study published in 2013 in Pharmacopsychiatry studied the thyroid functions of regular cannabis users and concluded that they had not been affected by their consumption.
In conclusion, one can only deplore the lack of studies devoted to the links between cannabis and thyroid disorders, while nevertheless welcoming the growing interest of researchers in this issue. As for the contradictions between the various studies, they are due as much to the fact that the samples are often too small to be truly significant as well as to the complexity of the cannabis itself. With such a wide variety of plants with such varied characteristics conclusions about cannabis and the thyroid are limited in their scope if cannabis varieties are not specified.
To put it another way, research on this issue simply separates people into two groups: those who use cannabis and those who do not. Consuming high CBD strains does not produce the same effects as high THC cannabis. Until researchers can separate their samples according to the cannabinoid content and variety of cannabis consumed, the studies will remain superficial and speculative. Therefore, if you suffer from any thyroid disorder and are tempted by a cannabis treatment, avoid self-medication and consult a specialist.
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