Modeling Growth Hormone Pulsatility

Dear everyone, I am looking for any reference for modeling hormone pulsatility in PK softwares. Would you recommend some good articles to me? Or any suggestion? Thanks in advance. I searched PubMed, and the Pulsatility can be modeled by some statistical models, which is not that easily to translate and implement in PK software, such as NONMEM, or ADAPT II. Jian --------------------------------- Bored stiff? Loosen up... Download and play hundreds of games for free on Yahoo! Games.

Dear Jian, We have good experience of a surge function. Surges, characterised by the parameters SA (surge amplitude), SW (surge width), T (clock time) and Pt (peak time), were used to define the function g(clock time) according to Eq. 4. g(Clock time) = SA / (((T - Pt) / SW)4 + 1) (Eq.4) This was presented by Nelamangala et al below (applied to LH surges). We applied it to ACTH / Cortisol. It was superior to (sum of) cosine functions for these hormones. Best regards, Mats Nelamangala N, Pechstein B, Erb K, Klipping C, Hermann R, Locher M, Derendorf H. Pharmacokinetic/Pharmacodynamic modeling of luteinizing hormone (LH) suppression and LH surge delay by Cetrorelix after single and multiple doses in healthy postmenopausal women. J Clin Pharmacol 2003; 43:243-251. Lonnebo A, Grahnen A, Karlsson MO. An integrated model for the effect of budesonide on ACTH and cortisol in healthy volunteers. Br J Clin Pharmacol. 2007 Feb 28; [Epub ahead of print] Mats Karlsson, PhD Professor of Pharmacometrics Div. of Pharmacokinetics and Drug Therapy Dept. of Pharmaceutical Biosciences Faculty of Pharmacy Uppsala University Box 591 SE-751 24 Uppsala Sweden phone +46 18 471 4105 fax +46 18 471 4003 [EMAIL PROTECTED] _____

Hi, Jurgen, Thanks for your reply and this reference. Fourier analysis is powerful but for non-stationary and non-linear data the basic assumptions of Fourier analysis are no longer valid. Therefore, I am looking for a method to describe both baseline circadian and pulsatility. Any further suggestions are appreciated. Jian Jurgen Bulitta <[EMAIL PROTECTED]> wrote: Dear Jian, A Fourier series with maybe 2-6 SIN and COS functions (and a baseline) should be able to describe multiple peaks. I do not know the shape of the pulses in your systems. Fourier series are very powerful to re-capture periodic functions empirically. If you estimate the coefficients of the SIN and COS functions as fixed effects, you should be fine in terms of overparameterization. One nice feature of the individual functions in a Fourier series is that these functions are orthogonal towards each other. Therefore, I would expect that the coefficients of the SIN and COS functions do not change (much), if you use 2, 4, or 6, etc. SIN/COS terms. One reference with an application: Krzyzanski W, Chakraborty A, Jusko WJ; Algorithm for application of Fourier analysis for biorhythmic baselines of pharmacodynamic indirect response models. Chronobiol Int; 2000; 17 77-93 Best regards Juergen ----------------------------------------------- Juergen Bulitta, PhD, Post-doctoral Fellow Pharmacometrics, University at Buffalo, NY, USA Phone: +1 716 645 2855 ext. 281, [EMAIL PROTECTED] ----------------------------------------------- --------------------------------- We won't tell. Get more on shows you hate to love (and love to hate): Yahoo! TV's Guilty Pleasures list.