From the Guidelines
THC may affect thyroid function, potentially decreasing thyroid hormone levels in some users by interacting with the endocannabinoid system, which has receptors in the thyroid gland. The effects of THC on thyroid function are not well understood and more research is needed to fully comprehend the relationship between THC and thyroid function. However, it is known that regular cannabis users might experience subtle changes in thyroid-stimulating hormone (TSH), T3, and T4 levels 1. For individuals with existing thyroid conditions, THC could potentially complicate management of their condition by interfering with medication effectiveness or masking symptoms. The effects seem dose-dependent, with heavier, long-term use more likely to cause noticeable changes. These interactions occur because cannabinoid receptors throughout the body, including in the hypothalamus and pituitary gland, influence the hypothalamic-pituitary-thyroid axis that regulates thyroid hormone production and release. Some key points to consider include:
- THC may decrease thyroid hormone levels in some users
- Regular cannabis users may experience subtle changes in TSH, T3, and T4 levels
- THC could potentially complicate management of existing thyroid conditions
- The effects of THC on thyroid function seem dose-dependent
- Cannabinoid receptors influence the hypothalamic-pituitary-thyroid axis Anyone with thyroid disorders who uses cannabis should inform their healthcare provider to ensure proper monitoring of thyroid function and appropriate adjustment of any thyroid medications if necessary 1.
From the Research
THC Effects on Thyroid
- The effects of THC on thyroid function are not fully understood, with some studies suggesting a potential impact on thyroid hormone levels, while others find no significant association 2, 3.
- A 2017 study found that recent marijuana use was associated with lower levels of thyrotropin (TSH) and positive anti-thyroperoxidase antibody (TPOAb) compared to nonusers and past users 2.
- In contrast, a 2013 study found that chronic cannabis abuse did not have a significant impact on thyroid function, with all tested patients having TSH, total T3, and free T4 levels within the population reference range 3.
- A 2022 review of the effects of cannabis and cannabinoids on the endocrine system found that acute use of THC may lower thyroid hormone levels, while chronic use may blunt the stress response 4.
- A 2021 study found that cannabis abuse did not significantly alter thyroid hormones in male patients, possibly due to the development of tolerance 5.
Thyroid Hormone Levels
- Studies have reported varying effects of THC on thyroid hormone levels, including decreased TSH levels 2 and no significant changes in T3 and T4 levels 3, 5.
- The 2022 review suggested that THC may affect thyroid hormone levels, but the evidence is limited and more research is needed to fully understand the relationship between THC and thyroid function 4.
Clinical Implications
- The potential impact of THC on thyroid function highlights the need for further research to understand the relationship between cannabis use and thyroid health 2, 3, 4.
- Clinicians should be aware of the potential effects of THC on thyroid hormone levels and consider monitoring thyroid function in patients who use cannabis, particularly those with pre-existing thyroid conditions 2, 4.