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Lymphocytic Hypophysitis (림프구성 뇌하수체염) — QSP Model

Disease: Lymphocytic Hypophysitis (LyH)
Category: Autoimmune (Pituitary)
ICD-10: E23.6 (Other conditions of pituitary gland)
Model version: 1.0 · Date: 2026-06-20

Overview

Lymphocytic Hypophysitis is a rare organ-specific autoimmune disease characterized by lymphocytic infiltration of the pituitary gland leading to progressive destruction of pituitary cells and multi-axis hypopituitarism. It is the most common form of primary hypophysitis and predominantly affects women in the peripartum period. Immune checkpoint inhibitors (anti-CTLA4, anti-PD1) represent a major iatrogenic cause.

Key Pathophysiology

Triggers (pregnancy / ICI / infection)
  ↓ molecular mimicry + HLA-DR3/4 susceptibility
APCs → MHC-II antigen presentation (PIT-1, RABPHILIN-3L)
  ↓
CD4+ T cell polarization (Th1/Th17) + CD8+ cytotoxic T cells
  ↓ B cell activation → plasma cells → Anti-Pituitary Antibodies (APA)
     + ADCC + complement deposition
Lymphocytic infiltration → Pituitary mass → Hormone deficiencies:
  • ACTH ↓  → secondary adrenal insufficiency (~70%)
  • TSH ↓   → central hypothyroidism (~40%)
  • FSH/LH ↓ → hypogonadism (~40%)
  • GH ↓    → adult GH deficiency (~30%)
  • PRL ↑   → stalk compression hyperprolactinemia (~50%)
  • ADH ↓   → diabetes insipidus (posterior, ~25%)

Mechanistic Map

QSP Mechanistic Map

Click the image to open the full-resolution SVG

Map Statistics:

  • 154+ nodes across 14 subgraph clusters
  • 14 biological subgraph clusters covering:
    1. Disease Triggers & Genetics
    2. Innate Immune System
    3. Adaptive Immune System (T & B cells)
    4. Cytokine & Chemokine Network
    5. Pituitary Anatomy & Pathology
    6. Hypothalamic Control
    7. HPA Axis
    8. HPT Axis
    9. HPG Axis
    10. GH/IGF-1 Axis
    11. Prolactin & ADH
    12. Drug PK
    13. Drug PD
    14. Clinical Endpoints

mrgsolve ODE Model

File: lhyp_mrgsolve_model.R

Model Structure: 22 ODE Compartments

Subsystem Compartments
Drug PK Pred_gut, Pred_central, Pred_periph, AZA_gut, AZA_plasma, RTX_plasma
Immune Naive T (Tn), Effector T (Te), Regulatory T (Tr), Naive B (Bn), Plasma cells (Bp), APA
Pituitary PitInf (inflammatory mass), PitFunc (functional cell mass)
HPA Axis ACTH, Cortisol
HPT Axis TSH, fT4
GH Axis GH, IGF1
HPG Axis FSH, LH, E2
PRL/ADH Prolactin, ADH

Key Equations

Cortisol Negative Feedback on ACTH (Hill kinetics):

ACTH_prod = kprod_ACTH × [1 - Emax × Cortisol^n / (IC50^n + Cortisol^n)] × PitFunc

Pituitary Functional Cell Mass:

dPitFunc/dt = -kpit_inflam × (Te + APA×0.01) × (1 - ImmunoSupp) + kpit_repair × PitFunc

Combined Immunosuppression:

ImmunoSupp = 1 - (1 - E_pred) × (1 - E_aza × 0.5)

5 Treatment Scenarios

# Scenario Description
S1 No Treatment Natural history over 2 years
S2 High-Dose Prednisolone 60→40→30→20→10→5 mg/day taper
S3 Pred + Azathioprine Steroid-sparing combination
S4 Rituximab ICI-associated LyH, anti-CD20 therapy
S5 Low-Dose Pred Suboptimal 10 mg/day maintenance

Calibration Data

Parameter Source Value
Prednisolone PK Czock et al. Clin Pharmacokinet 2005 ka=1.2/h, Vc=45L, CL=8.5L/h
ACTH deficiency prevalence Honegger et al. JCEM 2015 ~70%
TSH deficiency prevalence Honegger et al. JCEM 2015 ~40%
ICI-LyH steroid response Faje et al. JCEM 2014 ~50% remission
Rituximab Emax (B-depletion) Maloney et al. Blood 1997 0.90

Shiny App

File: lhyp_shiny_app.R

7 Interactive Tabs

Tab Content
1. Patient Profile Disease severity settings, treatment selection, LyH subtype
2. Drug PK Prednisolone, azathioprine, rituximab plasma concentrations
3. Pituitary Function Function score, mass index, hormone deficiency heatmap
4. Hormone Axes HPA (ACTH/Cortisol), HPT (TSH/fT4), GH/IGF-1, HPG (FSH/LH/E2)
5. Immune Dynamics T cells, B cells, APA, immune-pituitary phase plot
6. Clinical Endpoints Radar chart, adrenal crisis risk, summary table
7. Biomarker Trajectories Any variable with reference ranges, PRL/ADH 
# Launch the app
shiny::runApp("lhyp_shiny_app.R")

References

File: lhyp_references.md — 60 references in 9 sections

Section Count
Disease Overview & Epidemiology 5
Pathophysiology & Immunology 7
Clinical Presentation & Subtypes 4
Hormone Axis Dynamics & QSP 11
Treatment & Pharmacology 8
Checkpoint Inhibitor-Induced LyH 4
Biomarkers & Imaging 5
Mathematical & Systems Biology 7
Quality of Life & Outcomes 5

Files

lymphocytic-hypophysitis/
├── README.md                   ← This file
├── lhyp_qsp_model.dot          ← Graphviz mechanistic map (154+ nodes, 14 clusters)
├── lhyp_qsp_model.svg          ← SVG vector (scalable)
├── lhyp_qsp_model.png          ← PNG raster (150 dpi)
├── lhyp_mrgsolve_model.R       ← ODE model (22 compartments, 5 scenarios)
├── lhyp_shiny_app.R            ← Interactive Shiny dashboard (7 tabs)
└── lhyp_references.md          ← 60 references in 9 categories

Key Clinical Insights from Model

  1. ACTH deficiency is the most common and earliest deficit (~70% of LyH patients). Cortisol nadir often precedes clinical symptoms — screening is essential.

  2. Hyperprolactinemia from stalk compression may precede overt hormone deficiency, providing an early biomarker of pituitary infiltration.

  3. High-dose prednisolone taper achieves optimal outcomes by simultaneously suppressing lymphocytic infiltration AND reducing pituitary mass.

  4. Azathioprine (steroid-sparing) reduces cumulative corticosteroid exposure with comparable immunosuppressive efficacy over long-term follow-up.

  5. ICI-associated LyH responds poorly to corticosteroids alone — rituximab may be superior by depleting B cells producing APA.

  6. Posterior pituitary involvement (ADH deficiency → DI) is a poor prognostic marker indicating more severe infiltration and less reversible damage.

Dependencies

# Required R packages
install.packages(c(
  "mrgsolve",
  "dplyr",
  "ggplot2",
  "tidyr",
  "shiny",
  "shinydashboard",
  "plotly",
  "DT"
))

Part of the QSP Disease Model Library — automated daily model generation via Claude Code Routine
Model: Lymphocytic Hypophysitis v1.0 | Generated: 2026-06-20