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Module 13 · Anatomy & Physiology II
Inflammation resets the thermostat.
A calcium that would not sit still, a parathyroid hormone(PTH): Raises blood calcium by stimulating bone resorption. that never fit it, a vitamin D that stayed low, a cortisolA glucocorticoid involved in stress response, metabolism, and immune regulation. rhythm worn flat, a spineProminent ridge on the posterior scapula dividing it into supraspinous and infraspinous fossae. thin at 38 — five findings in 2013, blamed on perimenopause. This module builds the endocrine systemThe organ system consisting of glands that secrete hormones to regulate body functions. in anatomy’s own words, from ductless glands and the chemistry of a message to the hub at the baseA substance that accepts hydrogen ions (H⁺) or releases hydroxide ions (OH⁻). of the brain, the calcium guard detail and the two-glands-in-one on the kidney, puts every gland on its slide, and reads the five findings as set-points moved by one body-wide inflammatory signal — not five glands that failed.
The module’s question
A value the body defends minute to minute is drifting, and so are four others, each a little, each the same way. What has to be true about hormones, receptorsProteins located on the surface or inside cells that bind specific molecules (e.g., neurotransmitter and feedback for a working system to produce that — and how do you tell a dial that moved from a gland that failed?
Module trailer · about 2 minutes
Inflammation Resets the Thermostat — narrated, with captions and a full text description.
The module trailer. Watch it first.
Animation · in production · 2 min
Inflammation Resets the Thermostat
Two minutes: three calciums and three “normal” PTHs that never fit, a thermostat with a hand on the dial, five glands on five slides, a vitamin D line with one station tested, a morning that looked like an afternoon — and one ESR nobody read.
How every chapter works
- Animation (dark teal) — a short animated explainer, one idea each
- Slide (dark teal) — a still to study: a micrograph, a diagram or a map
- Explore (purple) — something to push on while you watch
- Game (purple) — a quick challenge
- Think (gold) — reason it out, then spot-check yourself with a few true/false questions; not graded
- Check (gold) — a quick H5P that scores itself
Read the chart and make a private prediction → the story → the scenes → sort your evidence → build your verdict → the finding. Nothing is graded, nothing is recorded, nothing is locked.
Where this module sits in Stina’s life
1986 · 11
Heat intolerance; the fevers begin
2010 · 35
Mom dies; teaching and hiding it
2013 · 38
DEXA low · calcium wandering · vitamin D 14 · cortisol flat · “perimenopause” · Clue #13
2015 · 40
Immunologist: MGUS
2020 · 45
Menopause
11 May 2026 · 51
FMF diagnosed · colchicine
Ochre = chart clue · Purple = diary entry.
The case this module reads
Thirty-eight, teaching in person and hiding it. A DEXA ordered for bone pain comes back below what her age allows. Three calciums that year — 10.6, 8.4, 9.3 — each beside a PTH the report calls normal and none on the side a working loop would put it. Vitamin D 14 in August. An 8 am cortisol of 7 and a 4 pm of 6. TSH at the top of its range. FSH 7 and a normal estradiolPrimary estrogen regulating female reproductive functions. — not perimenopause on paper — and an ESR of 44 filed under a different complaint. The endocrinologist’s word: perimenopause. The plan: calcium and vitamin D, recheck in six months. No one asked why a number the body guards this closely would wander at all.
Patient chart · Stina · Chart Clue #13
Bone
DEXA Z −2.3 at 38; alk phos 128
Calcium
10.6 / 8.4 / 9.3 · PTH 61 / 24 / 48
Vitamin D
25-OH D 14 ng/mL (August)
Cortisol
8 am 7 · 4 pm 6 — no peak
Not read
ESR 44 · FSH 7, estradiol normal
Seven chapters, seven decisions
Each chapter opens on the chart and ends with a verdict you build from evidence. Work them in order — later chapters assume the cards you collected earlier.
1
13.1 The Wandering Calcium
A value the body defends minute to minute is drifting. Before you can say why, you need to know what a gland is, how its message travels, and what tells it to fire. Then: one broken gland, her age — or a steady system being pushed from outside?
You decide: one broken gland, her age, or a system pushed from outside?
2 animations · 3 slides · 5 things to explore · 10 quick checks · 1 verdict
2
13.2 Messengers and Targets
Every lab on her chart measured the hormone in the tube. None measured what the cell heard. What has to be true about receptors, carriersMembrane proteins that transport substances across a cell membrane. and clearance for a hormone to be present in a normal amount and still be read wrong?
You decide: present in a normal amount — or misread?
3 animations · 2 slides · 5 things to explore · 10 quick checks · 1 verdict
3
13.3 The Thermostat: Negative Feedback
A thermostat holds a room at whatever number it is set to, even if someone has quietly moved the dial. Can a feedback loop work perfectly and still be wrong — and how would the labs look if it were?
You decide: can a loop work perfectly and still be wrong?
3 animations · 2 slides · 5 things to explore · 10 quick checks · 1 verdict
4
13.4 The Master and Its Boss
Several of her hormones are mildly off at once. Coincidence — or one command centre, sitting where the nervous and endocrine systems meet, being leaned on by a signal that acts on the brain?
You decide: coincidence, or one hub leaned on?
3 animations · 2 slides · 5 things to explore · 10 quick checks · 1 verdict
5
13.5 Guarding the Calcium
Her calcium wanders and her vitamin D stays low. One problem, or two — and which station on the calcium line would you test before accepting either answer?
You decide: one problem, or two windows on one loop?
4 animations · 1 slide · 5 things to explore · 10 quick checks · 1 verdict
6
13.6 Under Stress: Cortisol
A stress hormone built for brief, passing threats has been answering an alarm for years. Is a flat morning cortisol a lazy gland, an exhausted one — or a working axisSecond cervical vertebra; has the odontoid process (dens) for pivoting head (“no” motion). defending a set-point that has been worn down?
You decide: a lazy gland, an exhausted one, or a worn set-point?
3 animations · 2 slides · 5 things to explore · 10 quick checks · 1 verdict
7
13.7 Inflammation Resets the Set-Points
Five findings, each explained away alone, in a year when the ESR was 44 and nobody connected it. What single upstream force could move all of them at once without breaking a single gland — and how do you tell a moved dial from a failed gland on paper?
You decide: five findings, or one fire?
2 animations · 3 slides · 5 things to explore · 10 quick checks · 1 verdict
13.8 · Conclusion and Assessment
The module verdict, then everything to practice
13.9 · The Evidence Behind the Case
Check our reasoning against the literature
Stina’s diary
The entries behind this module
“The first time I believed them” (16) · “Nobody can tell” (36) · “Perimenopause” (38) · “Undetermined significance” (40) · “Fever of unknown origin” (41).
The original lectures and histology
Thirteen mini-lectures, six histology pages, one case study
Every original endocrine mini-lecture on bettybroadbent.com (Intro through Other Notable Hormones) is linked from the scene it belongs to, with the histology hub and self-guided journey, the six gland histology pages, the glossary and flashcard maker, the disease flip cards, Octavia’s hyperthyroidism case, and the Pancreas and Adrenal Medulla pages from the Digestive and ANS modules.
By the end you can
- Distinguish endocrine from exocrineGlands that secrete substances via ducts (e.g., sweat glands). glands and hormonal from neural control; locate the dedicated glands and the part-time secretors in anatomical terms; and name the three stimuliChanges in the environment that are detected by sensory receptors. that trigger hormone release.
- Classify hormones chemically, predict transport, receptorA structure that detects stimuli. location and mechanism from solubility, trace the cAMP(Cyclic AMP): Second messenger in many hormone signaling pathways. and PIP₂ pathways, and explain receptor regulation, hormone interactions, half-lifeTime for hormone levels to reduce by half. and clearance.
- Explain negative feedbackA control mechanism that reverses a change in the body to maintain homeostasis. and set-points, build the hypothalamic–pituitary–thyroid axis, follow thyroid hormone (TH): Includes T3 and T4, regulating metabolism. synthesis, and read a TSH/T4 pair to locate a lesion — or a moved set-point.
- Describe the hypothalamusA small but vital brain region controlling hormones, temperature, and autonomic functions. and both pituitary lobes structurally and functionally, including the portal system, the cell types of the pars distalis and the tropic cascades.
- Explain calcium homeostasisThe maintenance of a stable internal environment in the body. — PTH, calcitriolThe active form of vitamin D, promoting calcium absorption in the intestines. and calcitoninA hormone from the thyroid that lowers blood calcium levels by inhibiting osteoclasts. on bone, kidney and gut — and the vitamin D pathway from skinThe body’s largest organ, providing protection and regulation. to kidney.
- Describe the adrenal cortexOuter portion of the adrenal glands producing corticosteroids. zones and medulla, the controlsVariables that remain constant to ensure a fair test. of aldosteroneA hormone that increases sodium and water reabsorption in the kidneys, helping regulate blood pressu, the HPA axis and cortisol’s rhythm and actions, and the sympathomedullary response.
- Compare insulin and glucagonIncreases blood sugar by promoting glycogen breakdown., name the hormones of the kidney, heart, adipose, skin, gut, liverA large organ that produces bile, detoxifies blood, and stores nutrients., bone and thymus, and identify every gland in this module on a histology slide.
- Relate chronic inflammation to shifted endocrine set-points and distinguish, on paper, a gland that failed from a dial that moved.
Reliable information on rare diseases
NORD · NIH GARD · Orphanet · MedlinePlus Genetics: FMF · FMF & AID Global Association · Autoinflammatory Alliance · Global Genes · Amyloidosis Foundation
Stina has one rare disease. In the United States, about 1 in 10 people live with one of the more than 7,000 known rare diseases. These organizations are where patients, families and clinicians go for trustworthy information.
Hop to:
← Familial Mediterranean Fever — case home
All pages for Module 13 — The Endocrine System
13.0 Module Overview
13.1 The Wandering Calcium
13.2 Messengers and Targets
13.3 The Thermostat: Negative Feedback
13.4 The Master and Its Boss
13.5 Guarding the Calcium
13.6 Under Stress: Cortisol
13.7 Inflammation Resets the Set-Points
13.8 Conclusion and Assessment
13.9 Evidence Behind the Case
All Modules
- Anatomical Language, Membranes & Homeostasis
- Just Enough Chemistry
- The Cell & Its Transport
- Making Cells & Proteins
- The Integumentary System
- The Skeletal System
- The Muscular System
- Nervous Tissue & the Senses
- The Spinal Cord
- The Brain & the Blood–Brain Barrier
- The Autonomic Nervous System
- Special Senses (in developmentThe process of growth and differentiation.)
- The Endocrine System
- Blood
- The Heart
- Blood Vessels
- The Digestive System
- The Respiratory System
- The Urinary System
- Fluids, Electrolytes & Acid–Base Balance
- The Reproductive System
- The Immune System
List of terms
- parathyroid hormone
- cortisol
- spine
- endocrine system
- base
- receptors
- estradiol
- carriers
- axis
- exocrine
- stimuli
- receptor
- cAMP
- half-life
- negative feedback
- thyroid hormone
- hypothalamus
- homeostasis
- calcitriol
- calcitonin
- skin
- adrenal cortex
- controls
- aldosterone
- glucagon
- liver
- development