Four tiny glands sit on the back of the thyroid and do exactly one job: keep serum
calcium in range. PTH “Puts The calcium High.” Too much PTH → hypercalcemia → bones, stones,
groans and moans. Too little PTH → hypocalcemia → twitching, tetany and laryngospasm. And because
the glands live on the thyroid, every thyroid operation puts calcium at risk.
🧠 PTHPuts The calcium High in the blood. Low calcium → PTH up. High calcium → PTH down.
🔪 After a thyroidectomyCheck calcium at 24–72 h. 🧠 “Remove the T — check the C.”
🫘
WHERE THEY ARE & WHAT PTH DOES
STEP 1 · FOUNDATION
Get the anatomy and the one hormone right and both diseases fall out of it automatically.
🫘 Four glands on the BACK of the thyroid
Usually four glands — a superior and an inferior pair — each about the
size of a grain of rice, embedded in the posterior surface of the thyroid lobes. The number and exact
position vary between people, and the inferior pair varies the most, which is why they are the
easiest to injure in surgery.
🧠 P·C — Parathyroid controls Calcium. Nothing else on this page matters
until you can say that sentence.
⚙️ How PTH raises calcium — three doors
🧠 PTH = “Puts The calcium High.” Bone gives it, kidney keeps it, gut absorbs it.
🔁 The thermostat, in one paragraph
The parathyroid glands constantly taste the blood for ionized calcium.
Calcium falls → PTH rises → calcium comes back up
Calcium rises → PTH falls → calcium comes back down
PTH also drives phosphate out in the urine, which is why calcium and phosphate move in
opposite directions: Ca ↑ → PO₄ ↓ and Ca ↓ → PO₄ ↑.
🧠 Calcium and phosphate are on a see-saw. One goes up, the other goes down.
🧪 The number to hold in your head
Typical adult total serum calcium ≈ 9.0–10.5 mg/dL — a commonly used
adult range; always confirm the range your facility prints on the result.
Over 10.5 = hypercalcemia → think hyperPARAthyroid
Under 9.0 = hypocalcemia → think hypoPARAthyroid
Albumin matters: about half of serum calcium is bound to albumin, so a low albumin makes
total calcium look falsely low. Ionized calcium is the truer measure.
Magnesium matters: low magnesium blocks PTH release and blocks PTH working — you cannot
fix the calcium until the magnesium is fixed.
🧠 Low Mg = stuck calcium. Always look at the magnesium beside the calcium.
SEE ALSOFull electrolyte reference ranges are on
NG-134 (Mag · Calcium · Phosphate) and NG-003 (All Electrolytes Cheat Sheet).
🧠 The one-line rule for all four names
Hyper-PARA-thyroid= HYPERcalcemia (over 10.5)
Hypo-PARA-thyroid= HYPOcalcemia (under 9.0)
The gland name and the calcium go the same way. That is the opposite of
the thyroid pages, where TSH and the hormones go opposite ways — do not mix the two rules up.
🧠 Parathyroid: same direction. Thyroid TSH: opposite direction.
MoansFatigue, weakness, depression, confusion, coma at extremes
Plus hypoactive deep tendon reflexes and a shortened QT interval.
🧠 High calcium = the brake is jammed ON. Muscles, gut and brain all slow down.
🦴 What high PTH does to the skeleton
Chronically high PTH activates osteoclasts, which chew calcium out of bone.
The cortex thins, the trabecular lattice breaks up, and a fall — or sometimes no fall at all — produces
a pathological fracture.
🧠 The blood calcium is high because the bones are being robbed.
🪨 And where the calcium ends up — stones
🧠 Bed rest makes it worse. Immobility pulls even more calcium out of bone — get
them up and moving.
✅ Nursing care for HIGH calcium
1
Hydrate IV normal saline and oral fluids — often 3–4 L/day unless restricted. Dilution plus urinary excretion.
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2
Then a loop diuretic if ordered furosemide increases calcium excretion — only after the patient is rehydrated
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3
Mobilize weight-bearing keeps calcium in bone; strain all urine for stones
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4
Protect fall precautions, careful handling, cardiac monitoring
Expect drugs that push calcium down: bisphosphonates, calcitonin, and in
secondary/tertiary disease phosphate binders and vitamin D analogues.
Thiazide diuretics raise calcium — they are the wrong diuretic here.
🧠 Fluids first, furosemide second. Never diurese a dry patient.
SEE ALSOLoop vs thiazide diuretics are covered on
NG-113 and NG-198.
🍽️ Diet & teaching — hypercalcemia
Limit high-calcium foods and calcium-containing antacids while calcium is high
Push fluids; cranberry or other acidifying fluids may be suggested for stone prevention
Increase fiber for constipation
Stay active — avoid long periods of bed rest
Report bone pain, new confusion, or flank pain
🧠 Water, walking and fiber — the three free treatments.
🔻
HYPOPARATHYROIDISM · LOW CALCIUM
SIDE B · TOO LITTLE
Too little PTH and calcium falls. Nerves lose their brake and everything becomes TWITCHY.
⭐ Patho & causes — number one is surgical
Thyroidectomy or neck surgery — the glands are bruised, devascularised or removed. This is
the most common cause and it is the one you will see on the ward.
Autoimmune destruction of the parathyroids
Neck radiation
Hypomagnesemia — low magnesium stops PTH being released and stops it working
Congenital absence of the glands (e.g. DiGeorge syndrome)
Low PTH means calcium falls and phosphate rises — the see-saw again.
🧠 “Remove the T — check the C.” Every thyroid operation is a calcium event.
🚨 What low calcium looks like
Tingling / numbness around the mouth and in the fingertips and toes — the earliest symptom
Muscle twitching, cramps and spasm, progressing to tetany
Positive Chvostek’s and Trousseau’s signs
Hyperactive deep tendon reflexes
Prolonged QT interval → risk of dysrhythmia
Seizures
Diarrhea and abdominal cramping
Anxiety, irritability, confusion
Dry skin, brittle nails, thin hair, and in chronic disease cataracts
The one that kills is LARYNGOSPASM — stridor, a crowing sound, or difficulty speaking is an
airway emergency.
🧠 Low calcium = no brake. Nerves fire on their own — hence the twitching.
👋 The two bedside signs
🧠 CHeek = CHvostek. Trousseau = Twerk with the cuff. Trousseau’s is the more
specific of the two.
🔪 The post-thyroidectomy connection
Because the parathyroids sit on the posterior thyroid, they can be bruised,
have their blood supply interrupted, or be removed. Calcium characteristically falls
24–72 hours after surgery.
What you do: ask about tingling around the mouth and fingers at every assessment, check
Chvostek’s and Trousseau’s signs, monitor calcium levels, and keep IV calcium gluconate and
seizure/airway equipment readily available per unit protocol.
🧠 Tingling lips after neck surgery = calcium, and you say so out loud.
Replace calcium IV calcium gluconate for acute symptomatic hypocalcemia — on a pump, with continuous cardiac monitoring
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4
Then keep it up oral calcium + active vitamin D long term; correct magnesium if low
IV calcium cautions: give it slowly through a patent line — it causes severe tissue damage if it
extravasates. Watch the rhythm; it interacts dangerously with digoxin toxicity.
Therapy is usually lifelong after surgical loss of the glands
Report tingling, twitching, cramps or a change in the voice
🧠 Calcium needs vitamin D like a car needs a key.
🧪
THE NUMBERS & THE MONITOR
STEP 4 · CONFIRM
One scale, one ECG change each way. This is the whole lab section.
🧪 The calcium scale and the QT interval
🧠 Low calcium = LONG QT. High calcium = SHORT QT. Low and Long both start with L.
📊 Everything on one comparison
HYPERparathyroid 🔺
HYPOparathyroid 🔻
PTH level
HIGH (or inappropriately normal)
LOW
Serum calcium
HIGH — over 10.5 mg/dL
LOW — under 9.0 mg/dL
Serum phosphate
LOW
HIGH
Nerve & muscle
Sluggish — weakness, hypoactive reflexes
Twitchy — tetany, hyperactive reflexes
Bedside signs
None specific
Chvostek + Trousseau positive
Gut
Constipation, nausea, ulcers
Diarrhea, abdominal cramps
Bones
Pain, fractures, osteoporosis
Usually normal density
Kidneys
Stones, polyuria, thirst
Not typical
ECG
Shortened QT
Prolonged QT
The emergency
Hypercalcemic crisis — coma, arrhythmia
Laryngospasm and seizure
Core treatment
Fluids, then loop diuretic; bisphosphonates; parathyroidectomy
IV calcium gluconate; oral calcium + vitamin D
Wrong drug
Thiazides (they raise calcium)
Phosphate-raising foods and binderless diets
🧠 Read the middle column down, then flip every row. That is the right column.
⚠️ Traps students fall into
Mixing up the parathyroid rule (same direction as calcium) with the thyroid TSH rule
(opposite direction). They are different rules.
Forgetting to check magnesium when calcium will not correct.
Giving a diuretic before rehydrating a hypercalcemic patient.
Reaching for a thiazide in hypercalcemia — thiazides make it worse. Loops are the
calcium-losing diuretic.
Treating tingling lips after a thyroidectomy as “anxiety”.
🧠 If the calcium will not come up, look at the magnesium.
🔬 What gets ordered
Serum calcium (with albumin) and often ionized calcium
PTH level — interpreted together with the calcium, never alone
Phosphate and magnesium
Vitamin D level; renal function
24-hour urine calcium; imaging (sestamibi scan, ultrasound) to localize an adenoma
DEXA bone density scan
The single most useful pairing: a high calcium with a high (or non-suppressed) PTH is
hyperparathyroidism; a high calcium with a suppressed PTH points elsewhere, often to malignancy.
🧠 Never read a PTH without the calcium beside it.
💊
TREAT, TEACH, TEST YOURSELF
STEP 5 · CARE
Two directions, two toolkits — and one operation that can create the second problem.
🔪 Parathyroidectomy — before & after
Before: baseline calcium, phosphate and vitamin D; assess voice; discuss the likelihood of
needing calcium supplements afterwards.
After — the same neck-surgery rules as a thyroidectomy:
Airway first — stridor or noisy breathing is an emergency
Check behind the neck and on the pillow for bleeding
Assess voice quality hourly early on (recurrent laryngeal nerve)
Semi-Fowler’s 30–45°, neutral neck alignment, support the head when moving
Expect calcium to drop — “hungry bone” pulls calcium in rapidly after the tumor is removed
Serial calcium levels and repeated Chvostek/Trousseau checks
🧠 A · B · C · C — Airway, Bleeding, voice (Breathing), Calcium. Same four every time.
💊 Drug groups, sorted by direction
To LOWER calciumIV normal saline · loop diuretic (after rehydration) ·
bisphosphonates · calcitonin · phosphate binders in CKD
To RAISE calciumIV calcium gluconate (acute) · oral calcium carbonate or
citrate · active vitamin D (calcitriol) · magnesium if it is low
Doses vary widely by indication and route — follow the order and your facility
protocol rather than a remembered number.
🧠 Saline dilutes it, loops dump it, bisphosphonates lock it back in bone.
❌ Absolute nevers
Never give IV calcium fast or through a questionable line — extravasation causes
severe tissue necrosis.
Never give IV calcium to a digoxin-toxic patient without specific direction — it can
precipitate a fatal arrhythmia.
Never use a thiazide diuretic to treat hypercalcemia.
Never dismiss stridor, a crowing inspiration or a voice change after neck surgery.
Never keep a hypercalcemic patient on bed rest if they can safely be up.
🧠 Every one of these is a “which action would you question?” answer.
🧠 Quiz yourself — no peeking
8 questions with answers
Q1: A patient two days after a total thyroidectomy reports tingling around the mouth.
What do you assess next?
Chvostek’s and Trousseau’s signs, plus the serum calcium level — and notify the provider.
This is hypocalcemia from parathyroid injury, and the timing (24–72 hours) fits exactly.
Q2: Calcium 12.8 mg/dL. What is the first intervention?
Fluids — IV normal saline and oral intake. Rehydrate first; a loop diuretic only comes
after the patient has volume on board.
Q3: Which diuretic is wrong in hypercalcemia, and why?
A thiazide. Thiazides increase calcium reabsorption and raise serum calcium. Loop
diuretics do the opposite.
Q4: Describe Trousseau’s sign.
Inflate a blood pressure cuff above systolic pressure for about three minutes. A positive
sign is carpal spasm — the fingers extend and draw together and the thumb pulls across the palm.
Q5: A hypocalcemic patient develops a crowing, high-pitched inspiration. What is your
first action?
Treat it as laryngospasm — an airway emergency. Call for help, stay with the patient,
prepare emergency airway equipment and anticipate IV calcium gluconate.
Q6: Which set fits hyperparathyroidism — high Ca/low PO₄, or low Ca/high PO₄?
High calcium and low phosphate. PTH raises calcium and dumps phosphate in the urine.
Hypoparathyroidism is the mirror: low calcium, high phosphate.
Q7: Why must you check magnesium in a patient whose calcium will not correct?
Low magnesium both suppresses PTH release and blunts PTH’s effect at the tissues.
Until the magnesium is replaced, the calcium will not come up.
Q8: What is the ECG change with each calcium abnormality?
Hypocalcemia prolongs the QT interval; hypercalcemia shortens it. Low and Long both
start with L.
🧠 PTH = Puts The calcium HighBone releases it · kidney keeps it and dumps phosphate · gut absorbs it via vitamin D.
🔺 High Ca = SLUGGISHBones · Stones · Groans · Moans. Short QT. Fluids first, then a loop — never a thiazide.
🔻 Low Ca = TWITCHYChvostek + Trousseau, tetany, seizures, laryngospasm. Long QT. IV calcium gluconate.
🔪 Neck surgery = calcium watchFalls at 24–72 h. Tingling lips is the first clue. 🧠 “Remove the T — check the C.”