P-090. periovulatory gh levels are elevated due to increased gh production rate and burst frequency

GH status change during the menstrual cycle, with high periovulatory levels. Whether this reflects changes in secretion or clearance is unknown. We investigated 24 hour GH patterns in the early follicular (EF) versus the periovulatory (PO) menstrual phase in the same ten women (aged 24-34 years) with regular menses. Blood was sampled every 20 minutes and the data was evaluated by deconvolution analysis. There was no difference in basal secretion or half life of GH during the two phases. Burst frequency was significantly increased during the PO (13.3±0.5) compared to the EF (10.3±0.6) (p = 0.002). Interburst interval were different with shorter periods in the PO (107±5 min) compared to EF (134±8) (p = 0.004). There were no difference in mass (p = 0.13) or amplitude (p = 0.21) between the two phases. The production rate was significantly elevated during the PO (61±6 μg/L/24 h) compared to the EF (37±8) (p = 0.004). Serial regularity of GH patterns as estimated by approximate entropy statistics did not differ between the two phases. This study shows that the elevated GH levels during the PO phase of the menstrual cycle are due to increased GH production rate and burst frequency.