24-Hour profiles of circulating ghrelin and peptide YY are inversely associated in normal weight premenopausal women

► Circulating PYY was a significant predictor of ghrelin over 24 h in humans. ► Increases in circulating PYY were associated with decreases in circulating ghrelin. ► PYY may be modulating ghrelin secretion in normal weight women over a 24 h period. ► Findings substantiate experimental inferences that PYY modulates ghrelin secretion.