Impact of Low-Dose Melatonin Supplementation on Testosterone Levels in U.S. Adult Males

Amidst the rapid rise in melatonin supplementation, decreased testosterone levels amongst males in recent decades, and the unclear association between melatonin and the hypogonadal-pituitary-gland (HPG) axis, this study aimed to further examine the association between melatonin use and testosterone levels among men in a nationally representative sample.

U.S. men over the age of 18 surveyed from 2011-2016 via the National Health and Nutrition Examination Survey (NHANES) without missing demographic or pertinent health information were included in the analysis. A total testosterone (TT) level of less than 300 ng/dL was considered low. An average daily dose (ADD) was calculated to quantify participants' exposure to melatonin supplementation in the past 30 days.

Analysis included 7,656 participants after selection criteria. The median age of participants was 47 [31-63] years old; the median TT level was 389.9 [289 - 513.9] ng/dL. Melatonin intake was reported in 51 (0.7%) individuals with an ADD of 1 [0.4 - 3] mg/day. We found no association between melatonin intake in the past 30 days and low TT levels (OR = 0.958, 95% CI: 0.496 -1.850; P=0.898). As expected, increasing BMI (OR = 1.133, 95% CI: 1.122 - 1.144; P < 0.001) and older age (OR = 1.019, 95% CI: 1.016 - 1.022; P < 0.001) were associated with low TT levels.

Predominantly low-dose melatonin supplementation was not associated with low TT levels. Future studies are needed to better quantify the relationship between melatonin intake and low TT levels, especially in the setting of supratherapeutic doses and prolonged periods of exposure.