PSAT327 Can Cannabis Use Lead to Central Hypothyroidism

BACKGROUND: Marijuana has been legalized for medical use in 36 states and for recreational use in 18 states. Its effects on thyroid function and hypothalamic-pituitary-thyroid axis in humans is not known. CLINICAL CASE: 72 years old male presented to his primary care physician with occasional difficulty swallowing. He reported fatigue for 4-5 years, trouble falling asleep for 2 months, weight gain 8 pounds over last few weeks, occasional diarrhea, and intermittent episodes of heat intolerance. His past medical history included controlled type 2 diabetes mellitus, recurrent herpes simplex infection, arthritis of hip joints, short-term memory loss, anemia, carpal tunnel syndrome and benign prostatic hyperplasia. Medications included glimepiride, lisinopril, acyclovir, tamsulosin, finasteride, escitalopram. He had been smoking marijuana regularly since he was a teenager. He denied using any other supplements. His physical exam was normal with stable vital signs and normal BMI. His labs showed a low TSH (0.096 mcIU/mL, n: 0.358-3.8 mcIU/mL), normal free T4 (0.90 ng/dL, n: 0.76-1.46 ng/dL), normal total T3 (70 ng/dL, n: 60-180 ng/dL). Review of his labs showed low TSH for last 4 years progressively getting worse with normal free T4 levels. TSH-receptor antibody and TPO Antibody level were negative. His white cell count, hemoglobin and platelets were normal. His electrolytes, kidney function and liver function tests were also normal. Thyroid Ultrasound showed 2 small sub-centimeter hypoechoic nodules in the left thyroid lobe. Two years ago, a radioactive Iodine scan showed normal iodine uptake. A recent radioactive iodine uptake scan showed generalized decreased iodine uptake with no evidence of graves’ disease or toxic multinodular goiter. CONCLUSION: Currently there are no controlled studies on the effect of marijuana use on thyroid function in humans. A cross-sectional analysis using National Health and Nutrition Examination Survey (NHANES) from 2007 to 2012 showed recent marijuana use was significantly associated with lower levels of TSH but was not associated with thyroid dysfunction (1). This study suggests that marijuana use is associated with low TSH levels. This could be due to hypothalamic suppression of TSH or may indicate a protective role against hypothyroidism. Older studies in rodents showed that cannabis exposure may lead to suppression of TSH and hypothalamic function (2). The data related to human subjects is scarce. Therefore, pathophysiologic mechanisms are speculative, although animal data support potential mechanism of hypothalamic suppression. REFERENCES: 1. Malhotra S, Heptulla RA, Homel P, Motaghedi R. Effect of Marijuana Use on Thyroid Function and Autoimmunity. Thyroid. 2017;27(2): 167-173. 2. Hillard CJ, Farber NE, Hagen TC, Bloom AS. The effects of delta 9-tetrahydrocannabinol on serum thyrotropin levels in the rat. Pharmacol Biochem Behav. 1984;20(4): 547-550. Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m.