LAUSR

How the levels of circulating metabolites and bone turnover markers change during the menstrual cycle and with oral contraceptive use is unclear. A new study published in the Journal of Clinical Endocrinology and Metabolism examined plasma levels of specific factors in 28 eumenorrheic women and 10 oral contraceptive users at 7–9 time points across a menstrual or pill cycle. The plasma levels of the amino acids alanine, glutamine, threonine and tyrosine varied notably across the menstrual cycle. Furthermore, plasma levels of alanine, glutamine, glycine, proline and tyrosine, as well as the bone turnover markers Cterminal telopeptide of type 1 collagen and procollagen type 1 N propeptide, were lower in oral contraceptive users than in nonusers. These findings suggest that oral contraceptives might decrease collagen turnover, which could have implications for long term bone health.