Assessment of endogenous growth hormone pulsatility in gelded yearling horses using deconvolution analysis

Hypothesis/objectives: Defining normal Growth Hormone (GH) secretory dynamics in the horse is necessary to understand altered GH dynamics related to issues like welfare and disease. Animals and methods: Twelve healthy yearlings and two mature Standardbreds were used to quantify GH secretion. Endogenous GH half-life was determined after administration of 1.0 µg/kg BW GH releasing hormone (GHRH). Exogenous GH half-life was determined after administration of 20 µg/kg BW recombinant equine GH (reGH) with and without suppression of endogenous GH secretion by somatostatin infusion (50 µg/m2/h). Pulse detection algorithm (Cluster) as well as deconvolution analysis was used to quantify GH secretory dynamics based on GH concentration-time series sampled every 5 min from 22:00 till 06:00 h. In addition, reproducibility, impact of sampling frequency and influence of altering initial GH half-life on parameter estimates were studied. Results: Mean endogenous GH half-life of 17.7 ± 4.4 (SD) min and mean exogenous half-...