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MODULE 13:
ENDOCRINE SYSTEM
PART 2 OF 7
Stina carries dozens of hormonal signals in one bloodstream at once, yet each lands only where it is meant to. Understanding receptors explains why her calcium-regulating hormones can be present and still be misread.
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PATIENT CHART
STINA
THIS PART
Ages 47
PRESENTING WITH
Drifting serum calcium, low vitamin D, tired-but wired
ACTION TAKEN
IL-1β and IL-6 Blockers
DIAGNOSIS
Inflammation-Reset Endocrine Set-Points
CHART CLUES
COLLECTED AS YOU GO
Wandering Serum Calcium With Low Vitamin D
Calcium Hormones Normal — Yet the Value Still Drifts
Mildly Abnormal, Internally Consistent Endocrine Values
A Mild, Multi-Axis Pattern Pointing to One Upstream Hub
Low Vitamin D and an Off-Key PTH Around a Drifting Calcium
A Blunted, Flattened Morning Cortisol
Inflammation-Reset Endocrine Set-Points
Put your money down: If one bloodstream carries every hormone at once, why does each message reach only the right room?
At any moment Stina’s plasmaThe liquid component of blood. is ferrying thyroid hormone (TH): Includes T3 and T4, regulating metabolism., insulin, cortisolA glucocorticoid involved in stress response, metabolism, and immune regulation., PTH, and dozens more to the very same destinations, yet none of them scrambles. Before the videos, predict what keeps the messages sorted — and whether a hormone present in normal amounts could still land wrong.
Pick the answer you believe now. We’ll come back to it later!
One Hallway, Many Messages
Stina once asked how a single drop of blood could carry so many instructions without scrambling them. It is a fair question: at any moment her plasma is ferrying thyroid hormone, insulin, cortisol, PTH, and dozens more, all to the same destinations. Yet her thyroid signals don’t move her calcium, and her calcium signals don’t touch her thyroid. The bloodstream is a shared hallway; the messages still reach the right rooms.
Polar versus Nonpolar
Solubility decides everything about a hormone.
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Single Choice: Which statement about polar versus Nonpolar is correct?
The Peptide and Amine Hormones
Water-soluble messages that travel free.
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Drag the Words: Match each term to its role in the Peptide and Amine Hormones.
The Steroid Hormones
Fat-soluble messages that need a ride.
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The Steroid Hormones
Transport and the Thyroid Exception
Carriers that shuttle, protect, and pace release.
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Mark the Words: Mark the words that describe transport and the Thyroid Exception.
Two Chemistries, Two Ways to Knock
They reach the right rooms because of receptorsProteins located on the surface or inside cells that bind specific molecules (e.g., neurotransmitter. A hormone is a chemical messenger released into the blood to act on distant target cellsCells with specific receptors for a hormone., but only cellsThe basic structural and functional units of life. bearing the matching receptorA structure that detects stimuli. respond — the rest ignore it entirely. The two main hormone classes work differently: steroid hormones (like cortisol and active vitamin D) are lipid-soluble, slip through the membrane, and change gene expression directly, so they act slowly but durably; peptide hormones (like PTH) can’t cross the membrane, so they knock on surface receptors and trigger fast second messengers inside. This matters for Stina because the issue may not be how much PTH she makes but how her target cells — bone, kidney, gut — are reading it while inflammation reshapes their responsiveness.
Lock and Key
Why the right cell hears the message.
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Multiple Choice: Choose the best answer about lock and Key.
Balance in the Blood
Made, used, and cleared — steadily.
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Sort the Paragraphs: Put the steps of balance in the Blood in the right order.
Two Chemistries, One Bloodstream
How a hormone is built decides how it works.
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Dialog Cards: Flip the cards to review two Chemistries, One Bloodstream.
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Present, But Possibly Misread
For Stina this is more than chemistry trivia. If a hormone can be present in perfectly normal amounts and still be ignored or misread by a target cell that has changed how it listens, then her near-normal PTH need not mean her calcium control is fine. Years of inflammation are exactly the kind of pressureThe force exerted by gases in the respiratory system, affecting airflow and gas exchange. that can retune how bone, kidney, and gut read the calcium hormones — so the question shifts from how much hormone she makes to how faithfully her tissues are hearing it.
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FINDING!
Calcium Hormones Present in Normal Amounts — Yet the Value Still Drifts
The sign to log is subtle: Stina’s calcium-regulating hormones keep testing near-normal, and yet her calcium wanders. Because a hormone acts only on cells carrying the matching receptor, and because that reading can shift under chronic inflammation, a normal hormone level does not guarantee a normal effect.
Confirm or refute your bet: If one bloodstream carries every hormone at once, why does each message reach only the right room?
Return to the bet. The bloodstream is a shared hallway and receptors are the room numbers, which is how dozens of messages travel together without scrambling — and it means a hormone can be present yet misread if the target cell’s lock or its second-messenger wiring has changed. For Stina, that reframes everything ahead: her calcium may be adrift not because a gland makes too little hormone, but because her tissues, under years of inflammation, are reading it differently.
Slide 7 Transcript
NEXT PART
Receptors decide who hears the message — but something has to decide when the message stops. That off-switch is negative feedbackA control mechanism that reverses a change in the body to maintain homeostasis., and it is the logic chronic inflammation can quietly reset.
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QUICK QUESTIONS
QUICK QUESTIONS
List of terms
- plasma
- thyroid hormone
- cortisol
- receptors
- target cells
- cells
- receptor
- pressure
- negative feedback