RESUMEN
BACKGROUND: Glutathione due to its favorable side effect of skin whitening has been used by cosmetic centers and by individuals buying it as an over the counter supplementation. Because of this, this compound is prone to misuse. To date, there are limited studies on the adverse effects of exogenous supplementation of glutathione.OBJECTIVE: To determine the prevalence of thyroid dysfunction among individuals taking oral and intravenous glutathioneDESIGN: Cross-sectional studyMETHODS:Healthy Filipino subjects, 21 to 50 years of age, currently taking oral or intravenous glutathione, with no preexisting/ known thyroid disease and history of radiation exposure, and not taking medications with known effect on thyroid function were included in the study. Blood extraction for thyroid function test and thyroid ultrasound were conducted.RESULTS: A total of 36 subjects were analyzed with a mean age of 36.3±8 years, 86 percent were female. High dose glutathione (1000mg or more per day) was taken in by nine subjects (25%) while 27 subjects (75%) took doses below the recommended range (less than 1000ng per day). The prevalence of abnormal thyroid function was 5.56 percent (n=2). Both cases were taking low dose glutathione supplementation. No abnormal thyroid function was seen with higher doses of glutathione. No significant relationship was found between the duration of glutathione supplementation with thyroid function status. Thyroid stimulating hormone (TSH) levels were slightly higher among those taking high dose glutathione (mean=1.08 versus 1.04, p=.81). There was no significant differences in the duration and dose of supplementation with the size of the gland.RECOMMENDATION:The direct effect of L-glutathione supplements on thyroid function must be established using a longitudinal prospective study design. We also propose a group to serve as a negative control during the comparisons.