Exocrine autodigestion layer (acute pancreatitis autocatalytic latch, large-reserve EPI, PERT rescue)

Acute pancreatitis is the R19 switch with an autocatalytic self-amplification (active trypsin activates trypsinogen). The autoactivation threshold rises with the protective inhibitor (SPINK1); a sub-threshold trigger decays safely but a supra-threshold trigger LATCHES — the self-sustaining basin is irreversible to any parameter move, so intervention is pre-threshold only. Chronic EPI is the mirror: a large reserve delays steatorrhea until ~90% acinar loss, and PERT restores digestion above demand.

The second Tier-3 primitive: an AUTOCATALYTIC element — the §2 R19 switch ds/dt = g·s − s³ + h with a self-amplification term (active trypsin activates trypsinogen), vendored single-source as autoactivation_threshold / autodigestion_latched in the substrate. The first reading is the autoactivation threshold and its dependence on protection: the trigger needed to ignite the cascade rises with the protective inhibitor, so SPINK1 raises it while a gain-of-function protease (PRSS1) or loss of the inhibitor lowers it — the hereditary-pancreatitis genetics as a shift of one threshold, not a separate mechanism. The decisive reading is that the cascade LATCHES: a sub-threshold trigger fires briefly and decays back to the inactive rest basin (safe), but a supra-threshold trigger crosses into a self-sustaining active basin held on by the autocatalytic +g·s term with the trigger REMOVED — irreversible to any parameter move, which is exactly why an established attack cannot be switched off pharmacologically and is managed by supportive care. That makes intervention PRE-threshold only, stated as a rule: remove the trigger before it crosses (relieve the gallstone obstruction, stop alcohol, lower triglycerides) or raise the protection, because a strong-enough inhibitor past the R19 spinodal abolishes the self-sustaining basin entirely so the same trigger now decays. The chronic sequel is the mirror image: repeated attacks destroy acinar mass, but a large secretory RESERVE delays exocrine pancreatic insufficiency (steatorrhea) until capacity falls past ~90% loss (DiMagno 1973), the adequacy monotone in residual capacity; treatment is replacement — pancreatic enzyme replacement (PERT) adds exogenous output, restoring digestion above the demand once enough is supplied. The threshold-rises-with-inhibitor, the irreversible supra-threshold latch (pre-threshold-only intervention), the strong-inhibitor reversibility, and the large-reserve EPI with PERT rescue are [V], the latch an exact R19 hysteresis [F], the >90%-loss reserve threshold a cited anchor [L]; the absolute trigger / inhibitor and digestive-demand scales (model units) and the established-disease outcomes — necrosis extent, organ failure (need a tissue-injury layer) — are [O] with stated obstacles, and cystic-fibrosis CFTR is gene-key (disease_wp owns the gene defect, this package owns the ductal-secretion dynamics).

Acute pancreatitis is mechanistically the richest disease in this package, and it needs the second Tier-3 primitive: an autocatalytic element, one that amplifies itself. The pancreatic zymogen cascade is the §2 R19 switch ds/dt = g·s − s³ + h with a self-amplification term — active trypsin activates more trypsinogen — so it is the same double well in which the active basin, once entered, feeds itself. Like every layer here it is derived from R19, no new dynamics, no fit; the one reserve anchor is the >90%-loss steatorrhea threshold.

The first reading is the autoactivation threshold and its dependence on protection. The trigger needed to ignite the cascade rises with the protective inhibitor: a strong pancreatic secretory trypsin inhibitor (SPINK1) raises the threshold, while a gain-of-function protease (PRSS1) or loss of the inhibitor lowers it — reproducing the hereditary-pancreatitis genetics as a shift of one threshold, not a separate mechanism.

The second reading is the clinically decisive one: the cascade latches. A sub-threshold trigger fires briefly and decays back to the inactive rest basin — safe. A supra-threshold trigger crosses into the self-sustaining active basin and stays there: the autocatalytic +g·s term holds it on with the trigger removed. The transition is irreversible to any parameter move — once over, lowering the trigger does nothing — which is precisely why an established attack cannot be switched off pharmacologically and is managed by supportive care.

That makes intervention pre-threshold only, and the model states it as a rule: remove the trigger before it crosses — relieve the gallstone obstruction, stop alcohol, lower triglycerides — or raise the protection, because a strong-enough inhibitor (past the R19 spinodal) abolishes the self-sustaining basin entirely, so the same trigger that would have latched now decays. Before the threshold the system is rescuable; after it, no parameter move reverses the latch.

The chronic sequel is the mirror image. Repeated attacks destroy acinar mass, but the gland has a large secretory reserve: exocrine pancreatic insufficiency (steatorrhea) appears only once capacity falls past roughly 90% loss — the digestive output stays adequate across most of the sweep and fails only at the deep end (DiMagno 1973). The adequacy is monotone in residual capacity:

And the treatment is replacement, not parameter-tuning: pancreatic enzyme replacement (PERT) adds exogenous secretory output, restoring digestion above the demand once enough is supplied.

Treatment (model reading). Acute pancreatitis -- the model predicts IRREVERSIBILITY past the autocatalytic threshold, so the lever is PRE-threshold: remove the trigger (relieve the gallstone obstruction, stop alcohol, lower triglycerides) BEFORE it crosses, and raise the protective inhibitor (a strong-enough inhibitor abolishes the self-sustaining basin); once established, only supportive care, because no parameter move reverses the latch. Chronic pancreatitis / EPI -- the lever is REPLACEMENT: PERT (exogenous enzyme) restores the secretory output above the digestive demand. Cystic fibrosis is gene-key (CFTR) -> disease_wp owns the gene defect while this package owns the ductal-secretion dynamics. Target directions [V]; absolute trigger/inhibitor thresholds, the demand scale, and established-disease outcomes [O].

The threshold-rises-with-inhibitor, the irreversible supra-threshold latch (pre-threshold-only intervention), the strong-inhibitor reversibility, and the large-reserve EPI with PERT rescue are forced by the substrate [V], with the latch an exact R19 hysteresis [F] and the >90%-loss reserve threshold a cited anchor [L]. What stays open [O], each with its obstacle: the absolute trigger / inhibitor and digestive-demand scales (model units needing clinical calibration), and the established-disease outcomes — necrosis extent, organ failure — which need a tissue-injury layer. Cystic fibrosis is gene-key (CFTR): disease_wp owns the gene defect while this package owns the ductal-secretion dynamics.