Figure 6.

A, Simulated impact of half-life (top to bottom) and secretory-burst waveform (interrupted curves, left to right) and on the resultant shape of hormone-concentration peaks (continuous curves). Instantaneous secretion (delta function) yields a sharp peak, from which elimination half-lives may be estimated directly by exponential regression (left column). Symmetric Gaussian (middle) and asymmetric gamma (right) secretory bursts widen the peak and slow the descent of the concentration curve. B, Mathematical formulation of a flexible generalized gamma-probability model of secretory bursts. The three-parameter gamma waveform encompasses both rapid initial Gaussian-like (approximately time-symmetric) hormone release and delayed continuing (time-asymmetric) secretion. The three β parameters confer full flexibility of burst shape.