Context. Ghrelin, an acylated peptide hormone secreted from the gut, regulates appetite and metabolism. Elucidating its pattern of secretion in the fed and fasted states is important in the face of the obesity epidemic.

Objective. To examine changes in circulating ghrelin and des-acyl ghrelin in response to meals and fasting using newly-developed two-site sandwich assays and sample preservation protocols to allow specific detection of full-length forms.

Design. Ten-min sampling for 26.5 h during a fed admission with standardized meals and on a separate admission during the final 24 h of a 61.5 h fast and continuing for 2.5 h after terminating the fast.

Setting. University Hospital General Clinical Research Center.

Participants. Eight male volunteers, Mean ± SD age 24.5 ± 3.7 yr; BMI 24 ± 2.1 kg/m².

Main Outcome Measure(s). Ten-min sampling profiles for ghrelin and des-acyl ghrelin, fed and fasting.

Results. Fed: ghrelin and des-acyl ghrelin showed similar dynamics; both were sharply inhibited by meals and increased at night. Fasting: ghrelin decreased to nadir levels seen post-prandially; des-acyl ghrelin remained near peak levels seen pre-prandially. Total full-length ghrelin (acyl + des-acyl) levels remained unchanged.

Conclusions. Meals inhibited secretion of both ghrelin and des-acyl ghrelin, yet long-term fasting inhibited acylation but not total secretion. Acylation may be regulated independently of secretion by nutrient availability in the gut, or by esterases which cleave the acyl group. These studies highlight the importance of stringent conditions for sample collection and evaluation of full-length ghrelin and des-acyl ghrelin using specific two-site assays.