A Platelet Cycle in Normal Individuals

SUMMARY Oscillation of the platelet count was found in 4 of 11 normal individuals. This finding suggests that platelet production in at least some normal individuals is controlled by a negative feedback circuit containing a time delay. This type of circuit is known to be capable of stable oscillation. The periods of oscillation were between 21 to 35 days and are similar to those found in cyclical thrombocytopenia. These and previous findings suggest that many physiological parameters might be oscillatory due to the action of normal homeostasis. Periodic disease could then result from the oscillation being rendered more apparent or from the system changing from damped to stable oscillation.