Evaluation of circulating irisin levels in healthy young individuals after a single 100,000 IU vitamin D dose.

Irisin is a newly discovered hormone produced by the muscle. This hormone is involved in glucose metabolism, muscle strength and energy expenditure. As vitamin D is also known as a key player in that field, we aimed to see if a single dose of 100,000 IU of vitamin D would modify circulating levels of irisin in 29 young adults. Irisin was determined with the Phoenix Elisa assay at day 0, day 3, day 7 day 15 and day 28 after the loading dose. If we observed a significant increase in 25(OH)D levels (from 19.8±8.4 ng/mL to 33.0±8.5 ng/mL), irisin levels remained constant throughout the study (median 104.5 ng/mL, with values ranging from 69.9 to 390.9 ng/mL). Interestingly, one subject presented irisin values that were three times higher than all the others.