More than 22 million Americans use marijuana, both medicinally and recreationally, according to the National Institute of Drug Abuse, and that number can be expected to rise as more states make its use legal. Cannabis is known to improve pain tolerance1 and can stimulate the appetite in patients whose illnesses and treatment regimens inhibit appetite.
Given the limited understanding of how marijuana affects the endocrine system, a group of researchers set out to discover whether marijuana has an effect on thyroid function and autoimmune conditions.
The team from the Albert Einstein College of Medicine and Maimonides Medical Center, both in New York, examined data from the National Health and Nutrition Examination Survey (NHANES) of adults who had thyroid laboratory results and responses to a questionnaire about marijuana use for frequency.2 Results were separated by those who had used it in the past (more than 30 days ago) or were current users (within the last 30 days).
“Our data analysis suggested that among recent marijuana users, the rate of TSH level within the normal range was significantly higher than the rate of TSH within the normal range of subjects who reported past use or never used marijuana,” study author, Roja Motaghedi, MD, told EndocrineWeb.
The researchers found that the most recent marijuana users were significantly less likely to exhibit elevated thyrotropin (TSH) and anti-thyroperoxidase antibody (TPOAb) levels than past users or non-users.2 Once the data were controlled for confounding factors, recent marijuana use still correlated with a TSH level below 5.6 IU/mL, although not with a negative TPOAb level.
Fortunately, the most recent users tended to be younger males,2 a group that does not typically suffer from diabetes or thyroid issues.
“However, data on amount and timing of marijuana use was collected from self-reported questionnaires and could be biased,” said Dr. Motaghedi, associate professor of clinical pediatrics at Albert Einstein College of Medicine, in New York. Some of the answers seemed to be exaggerated, and I would imagine some subjects did not report accurately due to privacy issues surrounding the topic.”
Dr. Motaghedi also noted that her team did not have information on which subjects might have active thyroid disease or what medications they might be taking, preventing them from going so far as to recommend marijuana as a thyroid or endocrine system treatment. The study also didn’t gather data on how frequently current cannabis smokers smoked, which potentially could have affected their bloodwork.
At this point, it is reasonable to say that people who should not be smoking marijuana include those who are obesity and/or have diabetes, said Elena Christofides, MD, an endocrinologist and editorial board member of EndocrineWeb.
“We know that activation of endocannabinoid receptors does increase hunger,” she said, adding that the effects go beyond appetite and include having an adverse impact on the metabolic system, including blood sugar and body weight.
Her assertion is bolstered by the National Institutes of Health’s the Coronary Artery Risk Development in Young Adults (CARDIA) study,3 which looked at marijuana and blood-sugar levels in 3,034 participants 25 years after they were first assessed for cardiovascular risks in the 1980s. Participants who indicated that they were still using cannabis had a 65% higher risk of prediabetes than those who were not. And, adults who said that they had smoked at least 100 times in their life had a 49% higher risk of prediabetes. The risk of cannabis use did not appear to extend to the development of type 2 diabetes.
However, several other studies have had results that contradict the CARDIA study findings. A Harvard Medical School study found lower fasting insulin levels and less insulin resistance among marijuana users4 and Michigan State University researchers analyzed eight different studies with findings that indicated a 30% reduction in diabetes risk among marijuana users.5
Dr. Christofides welcomes studies that focus on marijuana use, considering the drug’s popularity and increasing legal status.
“I’m glad to see that some of the prejudices about looking at marijuana use are going by the wayside,” she said. However, clinicians must be prepared to address the temptation for use as an educational opportunity.
She recommended that endocrinologists do the following:
1. Russo EB. Cannabinoids in the management of difficult to treat pain. Ther Clin Risk Manag. 2008;4(1):245–259.
2. Malhotra S, Heptulla RA, Homel P, Motaghedi R. Effect of Marijuana Use on Thyroid Function and Autoimmunity. Thyroid. 2016 Published online ahead of print. December 5, 2016.
3. Bancks MP, Pletcher MJ, Kertesz SG, Sidney S, Rana JS, Schreiner PJ. Marijuana Use and Risk of Prediabetes and Diabetes by Middle Adultood: the Coronary Artery Risk Development in Young Adults (CARDIA) Study. Diabetologia. 2015;58(12):2736-44.
4. Prenner EA, Buettner H, Mittleman MA. The Impact of Marijuana Use on Glucose, Insulin, and Insulin Resistance among US Adults. Am J Med. 2013;126(7):583-589.
5. Alshaarawy O, Anthony JC. Cannabis Smoking and Diabetes Mellitus: Results from Meta-analysis with Eight Independent Replication Samples. Epidemiology. 2015;26(4):597-600.