| Abstract: | Peripheral platelet counts of 5 healthy women and 5 healthy men were studied over 54 to 100 d to assess whether statistically significant fluctuations could be detected. Low amplitude fluctuations were found in 7 of the 10 individuals with mean periods of 28.3 +/- 3.4 d, using autocorrelation analysis. To understand the origin of such fluctuations, a simple linear feedback model of thrombocytopoiesis was formulated and quantitatively analyzed. This model, together with literature data on platelet-turnover in healthy individuals and patients with idiopathic thrombocytopenic purpura (ITP), predicts states in which oscillations are likely to occur and explains these as a result of optimum tuning of the feedback system to respond quickly to disturbances in the platelet pool. Both in healthy individuals and patients with cyclic thrombocytopenia, the typical periods of the fluctuations predicted by the model of about 25 d are in good agreement with the data. |
