Effect of marijuana use on thyroid function and autoimmunity.

BACKGROUND:

Marijuana is legalized for medical use in 24 states and for recreational use in five. However, effects of marijuana use on thyroid function and autoimmunity are unknown. Objective and hypotheses: We performed a cross-sectional analysis of data from the National Health and Nutrition Examination Survey (NHANES) conducted between 2007-2012 to assess the effects of marijuana on thyroid function and autoimmunity in users.

METHOD:

We included 5280 adults ages 18 to 69 years, who responded to questions related to marijuana use and had laboratory results related to thyroid parameters. Subjects were categorized as non-users (never used), past users (used prior to 30 days), and recent users (used within 30 days). Using NHANES normative cut offs for thyroid parameters, we compared recent users to non-users and past users, and calculated the odds ratios for the relative rate of clinically significant thyroid dysfunction in those groups. Multivariate logistic regression was then performed to control for confounders.

RESULTS:

Fifty four percent of subjects reported lifetime cannabis use with 15% using it recently. Univariate regression analysis showed that recent marijuana users had significantly lower frequency of elevated thyroid stimulating hormone (TSH) and positive anti-thyroperoxidase antibody (TPO-Ab) versus nonusers/past users. After controlling for confounders, recent marijuana use remained an independent predictor for TSH<5.6 µIU/mL (Odds ratio of 0.344 with 95% CI of 0.127-0.928; p = 0.04) but not for negative TPO-Ab.

CONCLUSION:

Recent marijuana use was not associated with thyroid dysfunction, but was significantly associated with lower levels of TSH.